This textbook is written for undergraduate students of medical and medical pedagogical faculties of medical higher educational institutions. Students should independently use the acquired skills and abilities in diagnosing syphilis and comparing the results of laboratory tests with the clinical picture. The publication of a textbook devoted to errors in the diagnosis of syphilis is long overdue. This work is the result of many years of work by the staff of the department and the Republican Skin and Venereological Clinical Hospital. The authors use a large amount of clinical data to analyze the mistakes made by doctors when diagnosing syphilis and to stress the special significance of clinical methods of examining a patient when detecting such diseases. In essence, the present work is an analysis of clinical reviews carried out by the authors and published by them earlier in various dermatovenerologic journals and collections. The generalized information about syphilis is essential for undergraduate medical students, who must have knowledge of the clinical manifestations of syphilis and their diagnosis.