Differential scanning calorimetry (DSC) has been employed to investigate the thermal changes caused by the anticancer alkaloid drug vinorelbine in dipalmytoylphosphatidylcholine (DPPC) bilayers. The total enthalpy change was increased by the presence of the drug molecule, indicating a partial interdigitation of the lipid alkyl chains. The presence of cholesterol in DPPC bilayers including vinorelbine induced an obstruction of the interdigitation, since cholesterol interrupts the upraise of enthalpy change. Vinorelbine's interdigitation ability and stabilizing properties with the active site of the receptor have been compared with those of similar in structure amphipathic and bulky alkaloid vinblastine. The obtained results may in part explain their similar mechanism of action but different bioactivity.