the biological and clinical characteristics of 238 children with acute lymphocytic leukemia (all) were studied for 13 years. the cellular immunophenotyping of samples from the bone marrow was performed by an immunocytochemical ultramicromethod. of the total of studied all, 81.4 % were phenotype b and 18.5 % phenotype t. 48.4 % of the children with b-all were 2-5 years old, whereas 65.9 % with t-all were 6 or over. no statistically significant differences were found when sex and colour of the skin were analyzed in relation to the cellular leukemic phenotype. on diagnosing the disease, 59.3 % of the patients with b-all showed figures of leukocytes in peripheral blood < 20x109/l, whereas in 61.4 % with t-all, the figures were higher than 50x109/l. it was observed a greater incidence of organomegaly, mediastinal adenopathies, hemorrhagic manifestations and initial infiltration of the central nervous system in patients with t-all compared with those suffering b-all. the differences were highly significant. these results proved that the leukemic phenotype in all in children could be considered as a positive or negative prognostic factor of the disease.