This review concerns to modification of muscle contractile system functioning by phallotoxins (phalloidin and its derivatives). Binding to actin in thin filament, phallotoxins can change active tension, the spectrum of mechanical relaxation times, ATPase activity, Ca2+ sensitivity. Under some conditions these changes are very pronounced (tens of percents). As a whole phallotoxins action has the following properties: 1) muscle specificity. Qualitatively different changes have been caused by phalloidin in skinned fibers of cardiac, skeletal and smooth muscle. These differences seem to reflect, at least partially, the differences in the muscle specific proteins of the thin filament: 2) dependence on physiological state of the contractile system (thin filament activation, cross-bridge cycle kinetics); 3) specificity in action of different phalloidin derivatives. Due to such properties phallotoxins suppose to be a probe some essential steps in contractile proteins interaction and a potentially power tool for study of mechanism of muscle contraction.