In vitro activities of 11 antimicrobial agents were determined using Etest (AB BIODISK, Solna, Sweden) against 37 clinical isolates of Mycobacterium marinum. The most potent agent (MIC(50,) 0.047 microg/mL) was trimethoprim/sulfamethoxazole, but only 91.9% would be categorized as susceptible. Several agents had a complete spectrum of activity including gatifloxacin (MIC(90,) 0.38 microg/mL), minocycline (MIC(90,) 2 microg/mL), tetracycline (MIC(90,) 2 microg/mL) and amikacin (MIC(90,) 3 microg/mL). The new glycylcycline, GAR936, had a similar potency (MIC(90,) 3 microg/mL) to that of the parent minocycline compound (MIC(90,) 2 microg/mL), but the range of MIC values extended to 24 microg/mL. Numerous options appear to exist for the contemporary therapy of M. marinum infections including some newer fluoroquinolones and derivatives of tetracycline (doxycycline, minocycline, GAR936).