Twelve adults with acute lymphatic leukemia, all but one of whom had relapsed while being treated with the usual antileukemic agents, were treated with daunorubicin and prednisone. Two complete and three partial remissions were obtained. The average duration of remission was 3 months. Daunorubicin was especially useful in prolonging survival in the pathologic type designated acute, rather than subacute, lymphocytic leukemia. Regardless of the initial response, no patient treated a second time with daunorubicin obtained a second remission. There are seven reports in the literature describing 19 adults with acute lymphatic leukemia treated with daunorubicin alone or with prednisone. Our results indicate a less favorable response to daunorubicin than did these earlier reports. However, daunorubicin does appear to be a useful agent in adults with acute lymphatic leukemia resistant to conventional leukemia therapy.