To better characterize the virological and cytogenetic features of Burkitt's lymphoma (BL) occurring in so-called low-incidence areas, biopsy specimens were collected from BL patients diagnosed and treated in France, and attempts were made to cultivate malignant cells in vitro in order to provide large amounts of tumour material for further laboratory investigations. Sixty new BL-derived lymphomatous cell lines have been established from 43 individuals: 24 Caucasians, 14 North Africans and five Africans. Of these, 27 lines (from 18 individuals) were established from non-Epstein-Barr virus (EBV)-associated BL tumours, indicating that the relative ease in cultivating BL malignant cells in vitro is not limited to EBV genome-containing BL tumours. Cytogenetic investigations showed that all the BL cell lines had one of the three 'BL translocations' - t(8;14), t(8;22) or t(2;8). An estimate of the frequency of each translocation, based on the analysis of 51 independent IARC BL cell lines gave the following results: t(8;14), 76%; t(8;22), 16%; t(2;8), 8%. This large panel of cell lines is now a valuable tool for analysing the various phenotypic characteristics of BL cells. Comparisons can be made between multiple lines of BL from high-, intermediate- and low-incidence areas; significant numbers of EBV genome-negative and -positive lines and of tumour cells taken at diagnosis and at various stages of the disease can also be compared. For molecular and immunological investigations, EBV-immortalized lymphoblastoid cell lines (LCL) were also established from non-malignant lymphocytes of BL patients. The 24 paired BL and LCL cell lines obtained so far will allow precise, controlled studies of the molecular consequences of chromosomal translocations and of the comparative susceptibility of BL and LCL to immune effectors.