The clinical characteristics of 31 patients (pts.) (17 boys, 14 girls, median age 12 11/12 years) with large cell anaplastic lymphoma (LCAL) have been evaluated. 17 of these pts. had originally been diagnosed as suffering from "malignant histiocytosis" ("MH") and were therefore included in the DAL-Histiocytosis X 83 study. Another 14 pts. with Ki-1 lymphomas were enrolled in the BFM-NHL therapy studies. According to Murphyclassification 24 pts. (77%) had stage III or IV disease and in general presented in a severe condition. The lymphatic system was involved in 28 pts., 8 pts. (26%) had skin infiltration. With regard to lymphoma involvement of lung, bones and bone-marrow were unexpectedly frequent. CNS involvement was seen in just one pt. Despite rather heterogeneous therapy approaches (ALL-schedules, DAL-HX 83 protocol for treatment of "MH", combination of B-NHL-BFM and AML-BFM schedules, CHOP, BFM protocols for B-NHL) 30 out of 31 pts. achieved clinical remission (CR). The only nonresponder died during bone marrow transplantation of septicemia. 4 pts. relapsed during therapy. 3 of them died, 1 during a BMT. 1 pt. achieved 2nd CR with a BFM-B-NHL protocol. 3 pts. experienced a late relapse, 1 died, 1 2nd CR was achieved, the third pt. is still alive after 2 further relapses disease-free for 3 years. 23 pts. (74%, 13 out of 14 of BFM-NHL therapy study, 10 out of 17 of DAL-HX 83 study, 1 pt. after BMT) are in 1st CR with a median observation time of 2 9/12 years (range 5/12 to 17 9/12 years).(ABSTRACT TRUNCATED AT 250 WORDS)