Data on the penetration of new quinolones into selected extravascular sites in humans, i.e., blister fluid, sputum, prostatic secretions, cerebrospinal fluid, aqueous humor, bone, prostate tissue, and cells, are reviewedand the data presented in tabular form. Published reports indicate that penetration into all sites, including intracellular sites, is high and exceeds that achievable for other commonly used antimicrobial agents, including penicillins, cephalosporins, and aminoglycosides. Available clinical treatment data support the expected favorable outcome predicted by the high extravascular concentrations achieved with quinolones.