The expression of the vascular cell adhesion molecule (VCAM‐1), recently identified as cytokine‐inducible ligand of the β1‐integrin VLA‐4, was investigated on normal and malignant haemopoietic precursors as well as on haemopoietic cell lines. VCAM‐1 was demonstrated on >20% blasts in 4/22 acute myeloid leukaemia (AML) and 6/10 acute lymphoblastic leukaemia (ALL) specimens but was absent from CD34⁺ normal bone marrow precursor cells. Interestingly, the VCAM‐1⁺ AMLs classified as M1 and M5 simultaneously expressed N‐CAM (CD56), a member of the immunoglobulin family. In ALL, VCAM‐1 expression was restricted to Calla⁺ CD19⁺ precursors of the c‐ALL subtype. VCAM‐1 was also found on some cell lines, mainly of the B‐lymphocytic type. Furthermore, in 13/20 chronic lymphocytic leukaemia (CLL) samples >20% of the CD19⁺ B‐lymphocytic precursors carried VCAM‐1, which seemed to correlate with more advanced disease. Therefore VCAM‐1 expression appeared to characterize leukaemic cells of the B‐cell lineage as well as a CD56⁺ subset of AML. Since its expression was clinically correlated with dermal infiltrates of leukaemic cells in AML and with advanced Rai stages in CLL, VCAM‐1 may play a role in enhanced adhesion of the malignant cells to tissues and/or to each other.