Exhibit 12.1

Advanstar, Inc.        Computation of Ratio of Earnings to Fixed Charges/Deficiency  In the Coverage of Fixed Charges by Earnings Before Fixed Charges

|                                                                             |                                                                             | Predecessor                          |         | Advanstar |       
|---------------------------------------------------------------------------- | --------------------------------------------------------------------------- | ------------------------------------ | ------- | --------- | ------
|
|
|
|
|
|
|
|Earnings before fixed charges:                                               |                                                                             |                                      |         |           |       
|                                                                             | Income (loss) before income taxes, extraordinary item and accounting change |                                      | $       | (13,458   | )     
|                                                                             | Portion of rents representative of interest factor                          |                                      |         | 1,798     |       
|                                                                             | Interest on indebtedness                                                    |                                      |         | 39,888    |       
|                                                                             |                                                                             |                                      |         |           |       
|                                                                             |                                                                             | Earnings (loss) before fixed charges |         |           | 28,228
|                                                                             |                                                                             |                                      |         |           |       
|Fixed charges:                                                               |                                                                             |                                      |         |           |       
|                                                                             | Portion of rents representative of interest factor                          |                                      |         | 1,798     |       
|                                                                             | Interest on indebtedness                                                    |                                      |         | 39,888    |       
|                                                                             |                                                                             |                                      |         |           |       
|                                                                             |                                                                             | Total fixed charges                  |         |           | 41,686
|                                                                             |                                                                             |                                      |         |           |       
|Ratio of earnings to fixed charges                                           |                                                                             |                                      |        |           |       
|                                                                             |                                                                             |                                      |         |           |       
|Deficiency in the coverage of fixed charges by earnings before fixed charges |                                                                             | $                                    | (13,458 | )         | $     
|                                                                             |                                                                             |                                      |         |           |       

---

QuickLinks