Systematic Stefansky's serodiagnostic test in the course of ulcero-mutilating acropathia reveals a frequent positivity (25/30 patients). Superinfection by atypical Mycobacterium of telluric extraction is considered. A delayed hypersensibility to several Mycobacterium antigens is proved to Mycobacterium kansasii, johnei, balnei. Perhaps, the same type of infection might exist in the course of chronic leg ulcers.