A glucose biosensor flow injection system was applied for measurement of liposome membrane permeability. Glucose was enclosed in the inner aqueous phase of liposomes, and release of the glucose upon addition of a biologically active substance was monitored with this sensor system. As an illustrative example, we estimated the membrane-disrupting activities of the bee venom melittin and the antibiotic gramicidin S using the present system. This procedure has certain advantages over the classical spectrophotometric determination of glucose, being rapid, simple and economical.