Instituting a free fare for ADA complementary paratransit service in the state of Illinois will expectedly increase the demand and associated costs of providing the specialized service. This paper proposes a method to estimate such demand and cost increases. Our results show an estimated average increase in annual ADA trips between 121 and 171 percent in the Chicago area. Given previous industry free-ride experiments, the latent demand exhibited by the large number of persons with disabilities living within ¾ mile of a fixed route, and the expected diversion of wheelchair riders currently using fixed routes, we believe it is not unreasonable to expect increases in ridership approaching 100 percent. Compared to the (2007$) baseline total statewide cost of $99.3 million, the estimated cost due to increased demand would be between $123.9 and $160.6 million.