Clinical trials are recognized as the standard of care for the cancer patient, and the randomized, controlled trial represents the most definitive method to determine the effectiveness or ineffectiveness of a cancer treatment. However, less than 3% of all eligible patients enter a clinical trial. Of the 437 physician members of the Illinois Cancer Center (ICC), 244 responded to a survey designed to determine factors that present a significant barrier to entering patients on clinical trials. Rigid protocol design was the primary deterrent to accrual, especially for medical oncologists. Surgeons, radiation oncologists, and medical oncologists differed with respect to several factors, including willingness to seek a clinical trial, tendency to treat patients off study, quality-of-life issues, and the belief that trials were too excessive in time commitment (P less than .05). Compared with hospital-based physicians, community oncologists had fewer patients on trial, were more likely to enter patients on the basis of age, and were more concerned about aspects of informed consent and the financial burden of a trial (P less than .01). One third of the physicians never pursued a clinical trial because of conflict with the priorities of individual care and excessive follow-up time. Fourteen percent indicated that they discouraged patients from participating in a clinical trial due to the risk of a patient receiving a placebo and patient follow-up requirements (P less than .05). Subgroups of physicians differ in their reluctance to accrue patients, and there are clusters of beliefs expressed by physicians concerning their clinical trial activity. Current conduct of clinical trials needs to be reassessed, and intervention studies are required to determine the best methodology to alter physician reluctance to pursue clinical trials.