Mevalonate pathway inhibitor lovastatin inhibited proliferation of human multidrug-resistant promyelocytic leukemia HL-60/ADR cells in vitro, with MRP-gene coded p190 mediated drug resistance, to a markedly lesser extent than that of the parental drug sensitive HL-60 cells and also that of the other human multidrug resistant (MDR-1, P-glycoprotein) myeloid leukemia cell line HL-60/VCR. The sensitivity of the examined human leukemia cell lines to the cytostatic activity of lovastatin correlated approximately with the potential of lovastatin to induce the characteristic cell cycle alteration (i.e. the accumulation of lovastatin-treated cells in the G0/G1 phase of the cell cycle). The P-glycoprotein positive HL-60/VCR cells and the parental drug sensitive HL-60 cells were more sensitive to this cell cycle alteration than the HL-60/ADR multidrug resistant leukemia cells with MRP drug resistance. Lovastatin (72 hours, 20 micromol) induced apoptosis and cell necrosis in HL-60 cells, apoptosis but not cell necrosis in HL-60/VCR cells and neither apoptosis nor necrosis in HL-60/ADR cells.