Authors have studied the intraocular penetration of a new antibiotic, pefloxacin in 35 patients (35 eyes). This study emphasizes the three main qualities of this recent quinolone in ophthalmology: wide spectrum adequate for the most pathogens commonly found in endophthalmitis. Very large penetration in the aqueous humour flow with an average level of 0.95 mu/ml, which is over the minimal inhibitory concentration for many bacterial infections and is equal to 25% of average serum level.