This review analyzes the pathogenetic factors of cryptogenic stroke, the results of investigations into secondary prevention, and current approaches to diagnostic criteria for this condition. The rate of cryptogenic stroke (stroke with no unspecified or identifiable cause) is 20 to 40%. A great deal of etiological factors leading to the development of cryptogenic stroke determine the extraordinary heterogeneity of this patient cohort; at the same time there is no universally accepted opinion as to the identification of cryptogenic stroke, its risk factors, and medical treatment. The conception of ischemic stroke with no identifiable cause of embolism and with clearer diagnostic criteria will be able to perform special studies in this group of patients, which will contribute to more differentiated and effective therapy and secondary prevention.