Clinical results of the treatment of malignant lymphomas with a high risk of relapse by dose intensification and autologous bone marrow transplantation are reported. Since 1988, 68 patients with a median age of 34 years (range 16 to 56 years) received dose intensification, including 25 non-Hodgkin's lymphomas in first remission (12 lymphoblastic or Burkitt's lymphomas and 13 large cell lymphomas with risk factors), 20 aggressive non-Hodgkin's lymphomas in chemosensitive relapse, and 23 Hodgkin's lymphomas in chemosensitive relapse. The calculated 3-year overall survival and relapse-free survival was 72% (CI: 57-82%) and 61% (CI: 47-73%) respectively. Treatment related deaths were seen in 4.4%. The median duration of hospitalization was 30 days (range 19-51 days). The relapse-free 3-year survival for the separate treatment groups was 80% for lymphoblastic and Burkitt's lymphomas in first remission, 77% for large cell lymphomas with clinical risk factors in first remission, 39% for aggressive non-Hodgkin's lymphomas in chemosensitive relapse, and 59% for Hodgkin's lymphomas in chemosensitive relapse. These excellent results were obtained with acceptable toxicity and justify the use of dose intensification for a group of young patients with high risk lymphomas.