BACKGROUND Infections during chemotherapy-induced granulocytopenia constitute a major threat to patients with malignant disorders. The aim of this study was to evaluate whether circulating granulocytes after chemotherapy have a normal expression of adhesion molecules or if the granulocytes, in addition to being present in low number, also present signs of qualitative alterations. METHODS We have investigated the time course of adhesion molecule expression (CD11b/CD18 and CD62L) and in vitro mobilization [responsiveness against N-formyl-methionyl-leucyl-phenylalanine (fMLP) for CD11b/CD18] by flow cytometry in circulating granulocytes after chemotherapy in 12 patients with haematological malignancies. Blood samples for analysis were drawn before chemotherapy and at time points when granulocyte counts were < 0.5, 0.5-1.0 and > 1.0 x 109 L-1. RESULTS The quantitative level, expressed as mean fluorescence intensity (MFI), of CD11b/CD18 was significantly higher and of CD62L significantly lower at granulocyte nadir than before chemotherapy. The in vitro responsiveness to fMLP was significantly reduced at the same time point. These alterations were restored to pretreatment values at the time of granulocyte count recovery. Granulocytes from patients with bacteraemia (n = 6) exhibited lower CD11b/CD18 MFI values after fMLP stimulation than non-bacteraemic patients after granulocyte count recovery. In addition, the MFI of CD62L was significantly lower both before chemotherapy and after granulocyte recovery in the bacteraemic group. CONCLUSIONS Chemotherapy induces qualitative alterations in circulating granulocytes with respect to adhesion molecule expression and mobilization, and these alterations are more pronounced in patients with accompanying bacteraemia.