In 53 patients undergoing cataract extraction, the authors measured pefloxacin and ofloxacin penetration in aqueous humour and lens. Cataract removal was performed at varying times after either the end of one-hour infusion of pefloxacin, ofloxacin per os in one time, or pefloxacin per os during 3 days. In the two first schemes, acme concentrations in aqueous humour are 1.45 mg/l for pefloxacin, 1.14 mg/l for ofloxacin. These concentrations reach the MIC90 of most bacteria usually involved in endophthalmia. The steady state concentrations of pefloxacin are between 6 and 7 mg/l during the first 12 h: they reach the MIC of 80% of Streptococci. There is no evidence of accumulation of pefloxacin in lens; lenticular concentrations of ofloxacin are very low and rapidly decrease.