The problem that occupies one of the central places in stellar astronomy, the study of variable stars, is comprehensively covered. All the main types of variable stars are considered with special attention to their evolutionary status, physical reasons for variability, the connection of studies of variable stars with the problems of studying the structure of the Galaxy. This edition has been revised taking into account the latest data by well-known specialists G. Richter and V. Wenzel. The book is distinguished by a clear presentation of the material and scientific rigor. For students of astronomical specialties and specialist astronomers working both directly in the field of stellar variability research and in related fields, as well as astronomy lovers.