OPC-17116 is a new fluoroquinolone with potent activity against aerobic and anaerobic organisms. We evaluated the susceptibilities of 200 clinical gonococcal isolates including organisms with plasmid and chromosomally mediated resistance to beta-lactams and tetracycline. The antibiotics studied included OPC-17116, ofloxacin, ciprofloxacin, penicillin, tetracycline, erythromycin, azithromycin, and ceftriaxone. All isolates tested were susceptible to the quinolone class of antibiotics. The MICs of ciprofloxacin, ofloxacin, and OPC-17116 for 90% of isolates tested were 0.004, 0.03, and 0.004 micrograms/ml, respectively. For organisms with chromosomally mediated resistance to penicillin and tetracycline, geometric mean MICs of all antibiotics including the quinolones were increased.