We report a woman in whom a slow-growing scotochromogenic strain of Mycobacterium was cultured from skin lesions. According to its phenotypic and biochemical characteristics we could predict only that it might be M. szulgai, M. scrofulaceum or M. gordonae. Polymerase chain reaction amplification of the hsp65 gene and subsequent restriction fragment length polymorphism analysis on the isolated strain showed that its restriction pattern differed from both M. scrofulaceum and other scotochromogenic species. Ninety-nine per cent similarity was detected between the isolated strain and M. gordonae by sequencing of the hsp65 gene. This result suggests that the isolated strain may be either a slow-growing scotochromogenic Mycobacterium most resembling M. gordonae or a novel mycobacterial species.