There is limited information available regarding the reasons cancer patients decide to enter clinical trials. To explore this issue, aggregate responses to the question, "Are you interested in learning about clinical trials for your condition?" obtained from > 115,000 cancer patients (or their families) who entered data into 1 of several proprietary decision-support programs embedded within approximately 100 well-established cancer-related Internet sites were analyzed. The percentage of patients (or their families) who expressed interest in learning about clinical trials ranged from as low as 21% (endometrial and cervix cancer patients > 80 years of age; n = 178) to as high as 85%0 (recurrent ovarian cancer patients, age 51-60; n = 842). Patients > 80 years of age, regardless of sex, tumor type, or status of disease, were considerably less likely to be interested in clinical trial information than younger individuals. Whereas there were no differences between males and females in their desire to obtain information, patients with self-declared more "serious conditions" (e.g., metastatic breast cancer, recurrent prostate cancer), and those with specific cancers having a widely recognized poor prognosis (e.g., nonsmall cell lung cancer), were more likely to request study information. In the current evaluation of a large database of individuals who elected to participate in 1 of several cancer-related decision-support programs, major differences in self-expressed interest in obtaining information regarding clinical trials was observed. Particularly notable was the reduced desire to gather such information among the very elderly, and the increased interest by patients with the most serious cancer-related conditions.