Patterns of the interaction between water-soluble polysubstituted fullerene derivatives (PFDs) and the lipid bilayer of phosphatidylcholine liposomes were investigated by applying triplet and fluorescent probes. Objective quantitative criteria have been proposed for the evaluation of membranotropic action of chemical substances, notably, fullerene derivatives that quench fluorescent probes with different localizations within the membrane. Thus, the defined criteria are the rate constants for the quenching of the fluorescence of triplet probes and the equilibrium constants for PFD-probe complexes, which characterize their stability. The localization of PFDs in the membrane was determined by comparing rate constants for the quenching of eosin phosphorescence and equilibrium constants for PFD-chromophore complexes. In addition, the efficiency of the interaction of PFDs with various sites of the phospholipid membrane has been seen to depend on the charge of addends that are attached to the polysubstituted derivatives.