A 15-month-old 27.7-kg sexually intact male Doberman Pinscher was examined because of multiple subcutaneous abscesses on the neck, trunk, and limbs that developed 2 months after a dog bite and were refractory to antibiotic treatment. Incubation of a biopsy specimen at 37 C on a Lowenstein-Jensen agar slant for 8 days yielded growth of a Runyon's Group IV mycobacterium, and disseminated subcutaneous Mycobacterium sp infection was diagnosed. The organism was identified as M fortuitum, and was susceptible to amikacin, doxycycline, cefoxitin, minocycline, trimethoprim/sulfadiazine, and sulfisoxazole. Lesions resolved after 8 months of treatment with doxycycline (5 mg/kg of body weight, PO, q 12 h). The cause of dissemination was unknown; however, delay in debridement of the bite wound and corticosteroid use in initial wound management may have potentiated dissemination.