EXHIBIT 21

SUBSIDIARY LIST

AS OF SEPTEMBER 22, 2006



|                                                                  |  |              |  |                                                                                   
|----------------------------------------------------------------- |  | ------------ |  | ----------------------------------------------------------------------------------
|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, LLC                                |  | Delaware     |  |                                                                                   
|                                                                  |  |             
|Subsidiaries of Rural/Metro Operating Company, LLC:               |  |              |  |                                                                                   
|                                                                  |  |             
|Aid Ambulance at Vigo County, Inc.                                |  | 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      |  |                                                                                   
|Myers Ambulance Service, Inc.                                     |  | Indiana      |  |                                                                                   
|North Miss. Ambulance Service, Inc.                               |  | Mississippi  |  |                                                                                   
|Professional Medical Services, Inc.                               |  | Arkansas     |  |                                                                                   
|RMFD of New Jersey, Inc.                                          |  | Delaware     |  |                                                                                   
|R/M Partners, Inc.                                                |  | Delaware     |  |                                                                                   
|Rural/Metro Communications Services, Inc.                         |  | Delaware     |  |                                                                                   
|Rural/Metro Corporation                                           |  | Arizona      |  | Rural/Metro Ambulance Service, AMT, Arizona Medical
Transport, Tri-City Med       
|Rural/Metro (Delaware) Inc.                                       |  | Delaware     |  |                                                                                   
|Rural/Metro Logistics, Inc.                                       |  | Delaware     |  |                                                                                   
|Rural/Metro Mid-Atlantic, Inc.                                    |  | Delaware     |  |                                                                                   
|Rural/Metro of Colorado, 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
|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      |  | CareTrans; CareTrans Medicoach Services; SW General
Services                      
|The Aid Company, Inc.                                             |  | Indiana      |  |                                                                                   
|                                                                  |  |             
|Subsidiaries of Rural/Metro Corporation (an Arizona corporation): |  |              |  |                                                                                   
|                                                                  |  |             
|R/M Management Co., Inc.                                          |  | Arizona      |  |                                                                                   
|R/M of Mississippi, Inc.                                          |  | Delaware     |  |                                                                                   



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|                                                     |  |            |  |                                                    
|---------------------------------------------------- |  | ---------- |  | ---------------------------------------------------
|RMC Corporate Center, L.L.C. (1%)                    |  | Arizona    |  |                                                    
|RMC Insurance Ltd.                                   |  | Barbados   |  |                                                    
|Rural/Metro Corporation of Florida                   |  | Florida    |  |                                                    
|Rural/Metro Corporation of Tennessee                 |  | Tennessee  |  |                                                    
|Rural/Metro Fire Dept., Inc.                         |  | Arizona    |  | Rural/Metro Fire Dept.; Rural/Metro Fire
Department
|Rural/Metro of Alabama, Inc.                         |  | Delaware   |  |                                                    
|Rural/Metro of Arkansas, Inc.                        |  | Delaware   |  |                                                    
|Rural/Metro of California, Inc.                      |  | Delaware   |  |                                                    
|Rural/Metro of Georgia, Inc.                         |  | Delaware   |  |                                                    
|Rural/Metro of Indiana, Inc.                         |  | Delaware   |  |                                                    
|Rural/Metro of Kentucky, 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 South Carolina, Inc.                  |  | Delaware   |  |                                                    
|Rural/Metro of South Dakota, Inc.                    |  | Delaware   |  |                                                    
|Rural/Metro Protection Services, Inc.                |  | Arizona    |  |                                                    
|Rural/Metro Texas Holdings, Inc.                     |  | Delaware   |  |                                                    
|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.:   |  |            |  |                                                    
|                                                     |  |           
|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/Southwest                                   
|                                                     |  |           
|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. (50%)              |  | Delaware   |  |                                                    
|                                                     |  |           
|Subsidiaries of Rural/Metro Mid-Atlantic II, Inc.:   |  |            |  |                                                    
|                                                     |  |           
|Mobile Medical Transportation, Inc.                  |  | Maryland   |  |                                                    
|                                                     |  |           
|Subsidiaries of Mobile Medical Transportation, Inc.: |  |            |  |                                                    
|                                                     |  |           
|Choice American Ambulance Service, Inc.              |  | Virginia   |  |                                                    



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|                                                      |  |            |  |                            
|----------------------------------------------------- |  | ---------- |  | ---------------------------
|Subsidiaries of RMC Insurance, Ltd.:                  |  |            |  |                            
|                                                      |  |           
|RMC Corporate Center, L.L.C. (99%)                    |  | Arizona    |  |                            
|                                                      |  |           
|Subsidiaries of R/M of Mississippi, Inc.:             |  |            |  |                            
|                                                      |  |           
|Rural/Metro of Mississippi, Inc.                      |  | Delaware   |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro Corporation of Florida:   |  |            |  |                            
|                                                      |  |           
|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 Tennessee, 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 Logistics, Inc.:          |  |            |  |                            
|                                                      |  |           
|Rural/Metro Hospital Services, Inc:                   |  | Delaware   |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro of Alabama, Inc.:         |  |            |  |                            
|                                                      |  |           
|Medstar Emergency Medical Services, Inc.              |  | Delaware   |  |                            
|RISC America Alabama Fire Safety Services, Inc.       |  | Delaware   |  |                            
|Rural/Metro of Central Alabama, Inc.                  |  | Delaware   |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro of California, Inc.:      |  |            |  |                            
|                                                      |  |           
|Rural/Metro of San Diego, Inc.                        |  | California |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro of San Diego, Inc.        |  |            |  |                            
|                                                      |  |           
|San Diego Medical Services Enterprise, LLC (50%)      |  | California |  |                            
|                                                      |  |           
|Subsidiaries of Rural/Metro of Colorado, Inc.:        |  |            |  |                            
|                                                      |  |           
|Rural/Metro of Central Colorado, Inc.                 |  | Delaware   |  | Rural/Metro Ambulance      
|                                                      |  |           
|Subsidiaries of Rural/Metro of Georgia, Inc.:         |  |            |  |                            
|                                                      |  |           
|Coastal EMS, Inc.                                     |  | Georgia    |  |                            
|E.M.S. Ventures, Inc.                                 |  | Georgia    |  | Rural/Metro Ambulance      
|Medi-Cab of Georgia, Inc.                             |  | Delaware   |  |                            



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|                                                     |  |          |  |                                                                                      
|---------------------------------------------------- |  | -------- |  | -------------------------------------------------------------------------------------
|Subsidiaries of Rural/Metro of Indiana, Inc.:        |  |          |  |                                                                                      
|                                                     |  |         
|The Aid Ambulance Company, Inc.                      |  | Delaware |  | The Aid Company, Inc.; Rural/Metro
Ambulance                                         
|                                                     |  |         
|Subsidiaries of The Aid Ambulance Company, Inc.:     |  |          |  |                                                                                      
|                                                     |  |         
|Rural/Metro of Indiana, L.P. (1%)                    |  | Delaware |  |                                                                                      
|Rural/Metro of Indiana II, L.P. (1%)                 |  | Delaware |  |                                                                                      
|                                                     |  |         
|Subsidiaries of Rural/Metro of Kentucky, Inc.:       |  |          |  |                                                                                      
|                                                     |  |         
|Mercury Ambulance Service, Inc.                      |  | Kentucky |  |                                                                                      
|                                                     |  |         
|Subsidiaries of Rural/Metro of Nebraska, Inc.:       |  |          |  |                                                                                      
|                                                     |  |         
|Eastern Ambulance Service, Inc.                      |  | Nebraska |  |                                                                                      
|                                                     |  |         
|Subsidiaries of Rural/Metro of New York, Inc.:       |  |          |  |                                                                                      
|                                                     |  |         
|Corning Ambulance Service Inc.                       |  | 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; Rural/Metro
Helpline                                          
|                                                     |  |         
|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.:   |  |          |  |                                                                                      
|                                                     |  |         
|American Limousine Service, Inc.                     |  | Ohio     |  |                                                                                      
|                                                     |  |         
|Subsidiaries of Rural/Metro of Oregon, Inc.:         |  |          |  |                                                                                      
|                                                     |  |         
|Valley Fire Service, Inc.                            |  | Delaware |  | Rural/Metro Fire Department; Valley Fire
Service; Fire Service Research Co. of Oregon



4



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|                                                          |  |                |  |                                                 
|--------------------------------------------------------- |  | -------------- |  | ------------------------------------------------
|Subsidiaries of Rural/Metro of South Carolina, Inc.:      |  |                |  |                                                 
|                                                          |  |               
|EMS Ventures of South Carolina, Inc.                      |  | South Carolina |  |                                                 
|                                                          |  |               
|Subsidiaries of Rural/Metro of South Dakota, Inc.:        |  |                |  |                                                 
|                                                          |  |               
|Medical Transportation Services, Inc.                     |  | South Dakota   |  |                                                 
|                                                          |  |               
|Subsidiaries of Medical Transportation Services, Inc.:    |  |                |  |                                                 
|                                                          |  |               
|Sioux Falls Ambulance, Inc.                               |  | South Dakota   |  |                                                 
|                                                          |  |               
|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 Texas, 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       |  |                                                 
|                                                         
|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                           



5



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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%) |  |            |  |                                       
|                                                     |  |           
|San Diego Medical Services Enterprise, LLC           |  | California |  |                                       
|Member: Rural/Metro of San Diego, Inc. (50%)         |  |            |  |                                       



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