Between 1980 and 1983, 317 bone-marrow (BM) aspirates from 63 cases of Burkitt's lymphoma (BL) were studied with an in-vitro liquid culture monitoring system. BL cell lines were obtained in culture from 14 of 15 patients with cytologically positive marrow. The in-vitro monitoring system was shown to be useful regardless of Epstein-Barr virus (EBV) status, clinical status of patients and cytogenetic anomalies (8 t(8;14) 2 t(8;22) 2 When BM was cytologically normal or suspect, i.e., less than 5% BL cells, the in-vitro monitoring system was shown to be more sensitive than cytological examination in 25 of 56 cases (44%). The sensitivity of the test is 1/100 000, i.e., 3 logs inferior to the level of detection by cytology. When BM was harvested from all patients in complete remission after two months of chemotherapy, marrow purging proved not to be necessary (38/38 negative cultures); 7/10 of those patients will have been harvested to no purpose (no more than 30% with indication for autologous BM transplantation). When BM was harvested at relapse or in partial remission, the purging procedure was shown to be necessary in 9 of 16 cases (56%).