In this study we have demonstrated that the human promyelocytic leukaemia cell line (HL-60 cells) completely lack the biological functions of chemotaxis and degranulation. In addition, they were also unable to bind the anti-neutrophil monoclonal antibody NCD 1 which has been shown to inhibit these functions in the peripheral blood neutrophil. When HL-60 cells were induced to differentiate by culturing for 6 days at 37 degrees C in the presence of either 1.25% dimethylsulphoxide (DMSO) or 0.5% dimethylformamide (DMF), up to 35% bound NCD 1. Differentiated HL-60 cells are capable of chemotaxis, degranulation and these newly acquired functions were inhibited by NCD 1 in a manner similar to that seen for the peripheral blood neutrophil. The results correlate the appearance of an antigen on the cell surface of DMSO- or DMF-induced HL-60 cells with the acquisition of two specific cellular functions.