EXHIBIT 21

SUBSIDIARY LIST

AS OF NOVEMBER 14, 2007



|                                                                  |  |              |  |                                                                
|----------------------------------------------------------------- |  | ------------ |  | ---------------------------------------------------------------
|NAME                                                              |  | STATE        |  | NAMES UNDER WHICH ENTITY DOES BUSINESS                         
|                                                                  |  |             
|Overall Parent Company:                                           |  |              |  |                                                                
|                                                                  |  |             
|Rural/Metro Corporation                                           |  | Delaware     |  |                                                                
|                                                                  |  |             
|Subsidiaries of Rural/Metro Corporation (a Delaware corporation): |  |              |  |                                                                
|                                                                  |  |             
|Rural/Metro Operating Company                                     |  | Delaware     |  |                                                                
|                                                                  |  |             
|Subsidiaries of Rural/Metro Operating Company, LLC:               |  |              |  |                                                                
|                                                                  |  |             
|Aid Ambulance at Vigo County                                      |  | Indiana      |  |                                                                
|                                                                  |  |             
|Ambulance Transport Systems, Inc.                                 |  | New Jersey   |  |                                                                
|                                                                  |  |             
|Donlock, Ltd.                                                     |  | Pennsylvania |  | Rural/Metro Medical Services, Ltd.; Rural/Metro Ambulance, Ltd.
|                                                                  |  |             
|Medical Emergency Devices and Services (MEDS), Inc.               |  | Arizona      |  | MEDS & Logo                                                    
|                                                                  |  |             
|Metro Care Corp.                                                  |  | Ohio         |  | Rural/Metro Ambulance                                          
|                                                                  |  |             
|MO-RO-KO, Inc.                                                    |  | Arizona      |  |                                                                
|                                                                  |  |             
|Multi-Health Corp.                                                |  | Florida      |  |                                                                
|                                                                  |  |             
|North Miss. Ambulance Service, Inc.                               |  | Mississippi  |  |                                                                
|                                                                  |  |             
|RMFD of New Jersey, Inc.                                          |  | Delaware     |  |                                                                
|                                                                  |  |             
|R/M Partners, Inc.                                                |  | Delaware     |  |                                                                
|                                                                  |  |             
|Rural/Metro of Central Colorado, Inc.                             |  | Delaware     |  | Aurora Medical Services                                        
|                                                                  |  |             
|Rural/Metro Communications Services.                              |  | Delaware     |  |                                                                



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|                                                                  |  |            |  |                                                                                                                                                                                        
|----------------------------------------------------------------- |  | ---------- |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Rural/Metro Corporation                                           |  | Arizona    |  | Rural/Metro Ambulance Service, AMT, Arizona Medical Transport, Tri-City Med                                                                                                            
|                                                                  |  |           
|Rural/Metro (Delaware) Inc.                                       |  | Delaware   |  |                                                                                                                                                                                        
|                                                                  |  |           
|Rural/Metro of Greater Seattle, Inc.                              |  | Washington |  | Rural/Metro Ambulance                                                                                                                                                                  
|                                                                  |  |           
|Rural/Metro of Southern Ohio, Inc.                                |  | Ohio       |  | Rural/Metro Ambulance                                                                                                                                                                  
|                                                                  |  |           
|SW General, Inc.                                                  |  | Arizona    |  | Southwest Ambulance; Southwest Transportation Services; Southwest Medical Services; Tri- City Med                                                                                      
|                                                                  |  |           
|South Georgia Emergency Medical Services, Inc.                    |  | Georgia    |  |                                                                                                                                                                                        
|                                                                  |  |           
|Southwest Ambulance of Casa Grande, Inc.                          |  | Arizona    |  | Southwest Ambulance and Rescue of Arizona; SWARA                                                                                                                                       
|                                                                  |  |           
|Southwest Ambulance of New Mexico, Inc.                           |  | New Mexico |  |                                                                                                                                                                                        
|                                                                  |  |           
|Southwest General Services, Inc.                                  |  | Arizona    |  | SW General Services; Southwest Medical Billings Services                                                                                                                               
|                                                                  |  |           
|The Aid Company, Inc.                                             |  | Indiana    |  |                                                                                                                                                                                        
|                                                                  |  |           
|Subsidiaries of Rural/Metro Corporation (an Arizona corporation): |  |            |  |                                                                                                                                                                                        
|                                                                  |  |           
|E.M.S. Ventures, Inc.                                             |  | Georgia    |  | Rural/Metro Ambulance                                                                                                                                                                  
|                                                                  |  |           
|EMS Ventures of South Carolina, Inc.                              |  | Delaware   |  |                                                                                                                                                                                        
|                                                                  |  |           
|Medi-Cab of Georgia, Inc.                                         |  | Delaware   |  |                                                                                                                                                                                        
|                                                                  |  |           
|Medstar Emergency Medical Services.                               |  | Delaware   |  |                                                                                                                                                                                        
|                                                                  |  |           
|Mercury Ambulance Service, Inc.                                   |  | Kentucky   |  | Rural/Metro Alternative Transport Services; Rural/Metro of Bullitt County; Rural/Metro of Lexington; Rural/Metro of Louisville I; Rural/Metro of
Louisville II; Rural/Metro Tri-County;



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|                                                   |  |              |  |                                                                      
|-------------------------------------------------- |  | ------------ |  | ---------------------------------------------------------------------
|R/M Management Co., Inc.                           |  | Arizona      |  | Arizona Medical Transport; Red Van; Southwest Transportation Services
|                                                   |  |             
|RMC Corporate Center, L.L.C.                       |  | Arizona      |  |                                                                      
|                                                   |  |             
|RMC Insurance Ltd.                                 |  | Barbados     |  |                                                                      
|                                                   |  |             
|Rural/Metro Corporation of Florida                 |  | Florida      |  | Rural/Metro Ambulance                                                
|                                                   |  |             
|Rural/Metro Corporation of Tennessee               |  | Tennessee    |  | American Medical Transport                                           
|                                                   |  |             
|Rural/Metro Fire Dept., Inc.                       |  | Arizona      |  | Rural/Metro Fire Dept.; Rural/Metro Fire Department                  
|                                                   |  |             
|Rural/Metro of Central Alabama, Inc.               |  | Delaware     |  |                                                                      
|                                                   |  |             
|Rural/Metro of Nebraska, Inc.                      |  | Delaware     |  |                                                                      
|                                                   |  |             
|Rural/Metro of New York, Inc.                      |  | Delaware     |  |                                                                      
|                                                   |  |             
|Rural/Metro of Ohio, Inc.                          |  | Delaware     |  | Rural/Metro Ambulance                                                
|                                                   |  |             
|Rural/Metro of Oregon, Inc.                        |  | Delaware     |  |                                                                      
|                                                   |  |             
|Rural/Metro of San Diego, Inc.                     |  | California   |  |                                                                      
|                                                   |  |             
|Rural/Metro Texas Holdings, Inc.                   |  | Delaware     |  |                                                                      
|                                                   |  |             
|Sioux Falls Ambulance, Inc.                        |  | South Dakota |  |                                                                      
|                                                   |  |             
|The Aid Ambulance Company, Inc.                    |  | Delaware     |  | Rural/Metro Ambulance                                                
|                                                   |  |             
|W & W Leasing Company, Inc.                        |  | Arizona      |  |                                                                      
|                                                   |  |             
|Subsidiaries of Aid Ambulance at Vigo County, Inc: |  |              |  |                                                                      
|                                                   |  |             
|Rural/Metro of Indiana II, L.P. (99%)              |  | Delaware     |  |                                                                      
|                                                   |  |             
|Subsidiaries of Ambulance Transport Systems, Inc.: |  |              |  |                                                                      



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|                                                     |  |            |  |                              
|---------------------------------------------------- |  | ---------- |  | -----------------------------
|Keefe & Keefe Ambulette, Ltd.                        |  | New York   |  |                              
|                                                     |  |           
|Keefe & Keefe, Inc.                                  |  | New York   |  |                              
|                                                     |  |           
|Subsidiaries of Keefe & Keefe, Inc.:                 |  |            |  |                              
|                                                     |  |           
|Multi Cab Inc.                                       |  | New Jersey |  |                              
|                                                     |  |           
|Multi-Care International, Inc.                       |  | New Jersey |  |                              
|                                                     |  |           
|Subsidiaries of MO-RO-KO, Inc.:                      |  |            |  |                              
|                                                     |  |           
|Southwest Ambulance of Tucson, Inc.                  |  | Arizona    |  | Kords; Rural/Metro Ambulance
|                                                     |  |           
|Subsidiaries of North Miss. Ambulance Service, Inc.  |  |            |  |                              
|                                                     |  |           
|Rural/Metro Mid-South, L.P. (99%)                    |  | Delaware   |  |                              
|                                                     |  |           
|Subsidiaries of R/M Partners, Inc.:                  |  |            |  |                              
|                                                     |  |           
|Rural/Metro Mid-Atlantic II, Inc.                    |  | Delaware   |  |                              
|                                                     |  |           
|Subsidiaries of Rural/Metro Mid-Atlantic II, Inc.:   |  |            |  |                              
|                                                     |  |           
|Mobile Medical Transportation                        |  | Maryland   |  |                              
|                                                     |  |           
|Subsidiaries of Mobile Medical Transportation, Inc.: |  |            |  |                              
|                                                     |  |           
|Choice American Ambulance Service, Inc.              |  | Virginia   |  |                              
|                                                     |  |           
|Subsidiaries of RMC Insurance, Ltd.:                 |  |            |  |                              
|                                                     |  |           
|RMC Corporate Center, L.L.C. (99%)                   |  | Arizona    |  |                              
|                                                     |  |           
|Subsidiaries of Rural/Metro Corporation of Florida:  |  |            |  |                              



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|                                                      |  |            |  |                            
|----------------------------------------------------- |  | ---------- |  | ---------------------------
|Rural/Metro of North Florida, Inc.                    |  | Florida    |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro Corporation of Tennessee: |  |            |  |                            
|                                                      |  |           
|R/M of Tennessee G.P., Inc.                           |  | Delaware   |  |                            
|                                                      |  |           
|R/M of Tennessee L.P., Inc.                           |  | Delaware   |  |                            
|                                                      |  |           
|Subsidiaries of R/M of Tennessee G.P., Inc.:          |  |            |  |                            
|                                                      |  |           
|Rural/Metro Mid-South, L.P. (1%)                      |  | Delaware   |  |                            
|                                                      |  |           
|Rural/Metro of TN, L.P. (1%)                          |  | Delaware   |  | Rural/Metro Ambulance, L.P.
|                                                      |  |           
|Subsidiaries of R/M of Tennessee L.P., Inc.:          |  |            |  |                            
|                                                      |  |           
|Rural/Metro of Tennessee, L.P. (99%)                  |  | Delaware   |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro of San Diego, Inc.        |  |            |  |                            
|                                                      |  |           
|San Diego Medical Services Enterprise, LLC (50%)      |  | California |  |                            
|                                                      |  |           
|Subsidiaries of The Aid Ambulance Company, Inc.:      |  |            |  |                            
|                                                      |  |           
|Rural/Metro of Indiana, L.P. (1%)                     |  | Delaware   |  | Rural/Metro Ambulance      
|                                                      |  |           
|Rural/Metroof Indiana II, L.P.(1%)                    |  | Delaware   |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro of Nebraska, Inc.:        |  |            |  |                            
|                                                      |  |           
|Eastern Ambulance Service, Inc.                       |  | Nebraska   |  |                            



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|                                                     |  |          |  |                                                                                                              
|---------------------------------------------------- |  | -------- |  | -------------------------------------------------------------------------------------------------------------
|Subsidiaries of Rural/Metro of New York, Inc.:       |  |          |  |                                                                                                              
|                                                     |  |         
|Corning Ambulance Service                            |  | New York |  |                                                                                                              
|                                                     |  |         
|Eastern Paramedics, Inc.                             |  | Delaware |  | Rural/Metro Medical Services                                                                                 
|                                                     |  |         
|LaSalle Ambulance, Inc.                              |  | New York |  | Rural/Metro Medical Services                                                                                 
|                                                     |  |         
|Rural/Metro of Rochester, Inc.                       |  | New York |  | Rural/Metro Medical Services                                                                                 
|                                                     |  |         
|Towns Ambulance Service, Inc.                        |  | New York |  | Rural/Metro Medical Services                                                                                 
|                                                     |  |         
|Subsidiaries of Eastern Paramedics, Inc.:            |  |          |  |                                                                                                              
|                                                     |  |         
|Rural/Metro of Brewerton, Inc.                       |  | New York |  |                                                                                                              
|                                                     |  |         
|Subsidiaries of Rural/Metro of Rochester, Inc.:      |  |          |  |                                                                                                              
|                                                     |  |         
|Beacon Transportation, Inc.                          |  | New York |  | Rural/Metro Medical Services                                                                                 
|                                                     |  |         
|National Ambulance & Oxygen Service, Inc.            |  | New York |  | Rural/Metro Medical Services                                                                                 
|                                                     |  |         
|Subsidiaries of Rural/Metro of Ohio, Inc.:           |  |          |  |                                                                                                              
|                                                     |  |         
|Gold Cross Ambulance Services, Inc.                  |  | Delaware |  | Rural/Metro Ambulance                                                                                        
|                                                     |  |         
|Rural/Metro of Central Ohio, Inc.                    |  | Delaware |  | Rural/Metro Ambulance                                                                                        
|                                                     |  |         
|Rural/Metro of Northern Ohio, Inc.                   |  | Delaware |  | Rural/Metro Ambulance; Hess Ambulance Service; Physicians Lifeline, Inc.; Physicians/Medic Transport, Inc.;
|                                                     |  |         
|Subsidiaries of Gold Cross Ambulance Services, Inc.: |  |          |  |                                                                                                              
|                                                     |  |         
|Gold Cross Ambulance Service of Pa., Inc.            |  | Ohio     |  | Rural/Metro Ambulance                                                                                        
|                                                     |  |         
|Subsidiaries of Rural/Metro of Central Ohio, Inc.:   |  |          |  |                                                                                                              



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|                                                          |  |          |  |                                                 
|--------------------------------------------------------- |  | -------- |  | ------------------------------------------------
|Subsidiaries of Rural/Metro of Oregon, Inc.:              |  |          |  |                                                 
|                                                          |  |         
|Valley Fire Service, Inc.                                 |  | Delaware |  | Rural/Metro Fire Department; Valley Fire Service
|                                                          |  |         
|Subsidiaries of Rural/Metro Texas Holdings, Inc.:         |  |          |  |                                                 
|                                                          |  |         
|R/M of Texas G.P., Inc.                                   |  | Delaware |  |                                                 
|                                                          |  |         
|Rural/Metro of Arlington, Inc.                            |  | Delaware |  |                                                 
|                                                          |  |         
|Rural/Metro of Texas, Inc.                                |  | Delaware |  | Rural/Metro Ambulance                           
|                                                          |  |         
|Subsidiaries of R/M of Texas G.P., Inc.:                  |  |          |  |                                                 
|                                                          |  |         
|Rural/Metro of North TX, L.P. (1%).                       |  | Delaware |  | Rural/Metro Ambulance                           
|                                                          |  |         
|Rural/Metro of Texas, L.P. (1%)                           |  | Delaware |  | Rural/Metro Ambulance, L.P.                     
|                                                          |  |         
|Subsidiaries of Rural/Metro of Texas, Inc.:               |  |          |  |                                                 
|                                                          |  |         
|Rural/Metro of North Texas, L.P. (99%).                   |  | Delaware |  | Rural/Metro Ambulance                           
|                                                          |  |         
|Rural/Metro of Texas, L.P. (99%)                          |  | Delaware |  | Rural/Metro Ambulance.                          
|                                                          |  |         
|Subsidiaries of Southwest Ambulance of Casa Grande, Inc.: |  |          |  |                                                 
|                                                          |  |         
|Southwest Ambulance and Rescue of Arizona, Inc.           |  | Arizona  |  | Southwest Ambulance and Rescue of Arizona; SWARA
|                                                          |  |         
|Subsidiaries of The Aid Company, Inc.:                    |  |          |  |                                                 
|                                                          |  |         
|Rural/Metro of Indiana, L.P. (99%)                        |  | Delaware |  |                                                 



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LIMITED PARTNERSHIPS



|                                 |  |          |  |                                       
|-------------------------------- |  | -------- |  | --------------------------------------
|NAME                             |  | STATE    |  | NAMES UNDER WHICH ENTITY DOES BUSINESS
|                                 |  |         
|Rural/Metro Mid-South, L.P.      |  | Delaware |  |                                       
|                                 |  |         
|Rural/Metro of Tennessee, L.P.   |  | Delaware |  | Rural/Metro Ambulance                 
|                                 |  |         
|Rural/Metro of Indiana, L.P.     |  | Delaware |  |                                       
|                                 |  |         
|Rural/Metro of Indiana II, L.P.  |  | Delaware |  |                                       
|                                 |  |         
|Rural/Metro of North Texas, L.P. |  | Delaware |  | Rural/Metro Ambulance                 
|                                 |  |         
|Rural/Metro of Texas, L.P.       |  | Delaware |  | Rural/Metro Ambulance                 



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LLCS



|                                                     |  |            |  |                                       
|---------------------------------------------------- |  | ---------- |  | --------------------------------------
|NAME                                                 |  | STATE      |  | NAMES UNDER WHICH ENTITY DOES BUSINESS
|                                                     |  |           
|RMC Corporate Center, L.L.C.                         |  | Arizona    |  |                                       
|                                                     |  |           
|Members: RMC Insurance Ltd. (99%)                    |  |            |  |                                       
|                                                     |  |           
|Rural/Metro Corporation, an Arizona corporation (1%) |  |            |  |                                       
|                                                     |  |           
|Medical Transportation System, LLC                   |  | Maryland   |  |                                       
|                                                     |  |           
|San Diego Medical Services Enterprise, LLC           |  | California |  |                                       
|Member: Rural/Metro of San Diego, Inc. (50%)         |  |            |  |                                       
|                                                     |  |           
|Southwest General Services of Dallas, L.L.C.         |  | Delaware   |  |