Acute lymphoblastic leukemia with hand-mirror cells (ALL-HMC) was diagnosed in a 20-year old patient. Cytochemical investigations revealed a positive reaction for PAS and acid phosphatase. Lymphoid blast cells were studied with various monoclonal antibodies in order to determine their derivation and differentiation. The data obtained (positivity for Leu 9, OKT 11 and OKT 8) suggest that blast cells were of T lineage with OKT 8 phenotype. This report supports the phenotypic heterogeneity of ALL-HMC.