We evaluated the occurrence and the type of second malignancies among 74 patients with Hodgkin's disease (HD) and 407 patients with non-Hodgkin's lymphoma (NHL) who were treated at the National Cancer Center Hospital for more than one year. Fifteen patients developed a second malignancy. In 10 of these patients the second cancer was gastric cancer, but no cases of acute nonlymphocytic leukemia were encountered. The observed number of second cancers in females among the HD patients was significantly (p less than 0.005) greater than the expected incidence based upon the number of age-adjusted person-years both for all cancers and for stomach cancer. However, no significant differences between males and females in the NHL patients were found. Furthermore, no significant differences were seen in any of the groups between the observed and expected numbers of second malignancies according to the treatment.