This study examines the effects of the family of calcium-dependent phospholipids binding proteins (annexins) on the contractile properties of rat portal vein. We developed the new method of annexin's purification from pig stomach muscle. It found that in nanomolar concentrations annexins caused dose-dependent effects on phasic and tonic component of rat portal vein contractile activity. The frequency of spontaneous contractions was increased whereas the amplitude was decreased. At the same time we observed the rise of basal tone level of contractions. We suggested that annexins may change the contractile properties of vascular smooth muscle.