Patients were followed for about 10 years on average. New cancers occurred in 53 of the 1036 patients. Patients who had undergone transplants were almost four times as likely to develop second cancers than were patients in the general population. The most frequent types of second cancers were cancers of the skin (14 patients), mouth (7 patients), uterus or cervix (5 patients), thyroid gland (5 patients), breast (4 patients), or brain (3 patients). The older a patient was at the time of the bone marrow transplant, the higher the risk of developing a second cancer. In addition, patients who had received a medication called cyclosporin A seemed most likely to develop second cancers.