CP-99219 is a novel 7-[3-azabicyclo (3.1.0) hexyl] quinolone that possesses activity against a wide variety of aerobic and anaerobic pathogens. The disk diffusion test results (5-micrograms CP-99219 disks) were compared with CP-99219 minimum inhibitory concentrations (MICs) using 445 contemporary clinical isolates, including 210 strains that were resistant to ciprofloxacin (MICs, > or = 4 micrograms/ml). A high correlation was observed between methods (r = 0.97), and the proposed conservative zone diameter interpretive criteria were selected primarily from the regression equation as follows: susceptible at > or = 15 mm (< or = 2 micrograms/ml, preferred) and resistant at < or = 10 mm (> or = 8 micrograms/ml); or susceptible at > or = 19 mm (< or = 1 microgram/ml) and resistant at < or = 14 mm (> or = 4 micrograms/ml). Using these criteria, the occurrence of false-resistant and false-susceptible disk diffusion test results should remain rare (< or = 1.5%).