In 1990, the five leading causes of cancer death in men aged 65 and older were carcinomas of the lung, prostate, colon and rectum, and pancreas, and leukemia. For women in this age group, the five leading causes of cancer death were carcinomas of the lung, breast, colon and rectum, pancreas, and ovary. To determine the representation of the elderly in clinical trials, the 1992 accrual of the National Cancer Institute (NCI)-sponsored Clinical Cooperative Group treatment trials (which included more than 8000 elderly patients) for the aforementioned sites was compared with the 1990 incidence data from the NCI's Surveillance, Epidemiology, and End Results program. Of the male patients enrolled in the trials, an average of 39% were older than 65 (47.3% lung, 79.5% prostate, 47.5% colorectal, 45.6% pancreas, and 9.6% leukemia); whereas 25.9% of all women enrolled in trials were 65 or older (43.6% lung, 17.3% breast, 46.2% colorectal, 59.6% pancreas, and 35.4% ovary). With respect to incidence, older patients generally are underrepresented in cancer treatment trials. With the exception of the data on prostate cancer, each of the comparisons using the Z statistic gave probability values of less than 0.01. The most significant discrepancies between incidence and participation in cancer treatment protocols were noted for leukemia in males and breast cancer in females. Possible explanations for these findings include (1) a research focus on aggressive therapy, which may be unacceptably toxic to the elderly; (2) presence of comorbidity in the elderly; (3) fewer trials available specifically aimed at older patients; (4) limited expectations for long term benefits on the part of physicians, relatives, and the patients themselves; and (5) a lack of financial, logistic, and social support for the participation of elderly patients in clinical trials. Recognizing this situation, NCI recently sponsored a number of trials that specifically target the elderly. This paper describes the status of all major Phase II and III clinical trials that recently were closed, still are active, or now are in review that address the clinical care of this important segment of the U.S. population.