The antimicrobial agents amikacin and doxycycline, which are not conventionally considered for use in treatment of mycobacterial infections, inhibit growth of Mycobacterium fortuitum and Mycobacterium chelonei in vitro. Ten patients were treated with these drugs alone or in combination with some surgical procedure. Seven of the 10 patients were definitely cured by the therapy. Only one definite treatment failure occurred. Patients with infections due to M. fortuitum or M. chelonei that are susceptible in vitro to these drugs appear to benefit from chemotherapy.