The literature data on such severe and rare complications of chancre in primary syphilis as gangrene and phagedenic ulcer, that developing normally in the background of immunodeficiency patients, especially in alcoholics, are presented. Infection and the development of chancre significantly change the clinical manifestations of primary syphilis, which can lead to diagnostic errors. The clinical observation of the patient suffering from alcoholism, which had a diagnosis ofprimary syphilis chancre on the basis of complicated phagedenic ulcer, regional lymphadenitis, positive serological reactions, acute reaction to the beginning of specific treatment, is presented. The treatment with Benzylpenicillin sodium was performed and led to the scarring of the chancre.