Mycobacterium marinum is emerging as an important human pathogen in the United States. We report four cases incidentally diagnosed from culture of biopsy specimens of wrist lesions at a Connecticut inner city hospital between 1996 and 1999. There was no clear association with aquatic exposure and only one patient recalled prior trauma. All were successfully treated with ethambutol and rifampicin. The current literature on the epidemiology, clinical characteristics and management of Mycobacterium marinum infections is reviewed.