Evidence suggests that insurers limit access to clinical trials because of cost concerns. Denial of coverage for treatment in a clinical trial limits patient access to trials and could limit clinical research. Public and private efforts are underway to change these policies, but their status is unclear, although preliminary estimates suggest that such changes would not be expensive. Previous studies found that treatment costs in clinical trials are similar to costs of standard therapy; however, it is difficult to generalize from these studies. As part of the Cost of Cancer Treatment Study, an ongoing effort to produce generalizable estimates of the incremental costs of government-sponsored cancer trials, the authors are conducting a one-year retrospective study of costs for 1,500 cancer patients recruited from a randomly selected sample of institutions in the U.S. The results of the study should be of great interest to insurers and the research community as they consider permanent ways to finance cancer trials.