Acute lymphoblastic leukaemia of B-cell phenotype (B-ALL) is uncommon. We studied eight cases of B-ALL, investigating the clinical characteristics as well as the biological features. Cytology revealed a typical L3 profile in most cases, but in one case the morphological diagnosis was L2 and morphometric analysis indicated that the blasts in B-ALL were larger than in other ALLs. Cytogenetic study detected the typical translocations (8; 14) and (8; 22) in most of the cases. Abnormalities of the long arm of the chromosome 1 were found in four cases and a major aneuploidy was observed in one case. Cell-cycle analysis showed a high degree of proliferation with, in all cases, a small fraction of cells in G1 with low protein content (corresponding to early G1). All these biological characteristics must be related to the poor prognosis of this disease.