Pretreatment immunologic marker analysis in 152 adult and childhood patients of ALL and ALL/lymphoma employing multiple monoclonal antibodies and hetero-antisera revealed three major subgroups, i.e. T-ALL (37.7%), N-ALL (33.1%) and C-ALL (21.5%). The early age peak was absent, males predominated in all the subgroups and T-ALL had increased incidence of thymic mass. Leucocyte counts of 50,000 X 10(6)/l were equally frequent in the three groups. T-ALL showed marked heterogeneity by showing a variety of markers such as T-helper/inducer, T-suppressor/cytotoxic, p-24, Ia and CALLA. These results show a high prevalence of unfavourable prognostic factors in ALL in our geographic region which might be related to socioeconomic and/or environmental factors.