Experimental studies on rabbit eyes were performed to examine the penetration capacity of cefsulodin into the anterior chamber and the vitreous body. One group of animals was injected with 50 mg/kg body weight intravenously, the other group received 20 mg subconjunctivally. Samples of the anterior chamber and the vitreous body were taken from the anaesthetized animals after 15, 30, 60 and 120 min (6 eyes at each time). The corresponding serum concentrations were determined as well. Cefsulodin concentrations were measured microbiologically with agar diffusion tests. At each time studied, the antibiotic could be detected in the anterior chamber after intravenous injection. Concentrations ranged from 2 to 5.2 mg/l. Similar results were found after subconjunctival application. In no case the antibiotic was detectable in the vitreous body. The pharmacokinetics of cefsulodin in the rabbit eye seem to be comparable to the behaviour of other β-lactam antibiotics and aminoglycosides. As cefsulodin is able to penetrate into the anterior chamber, it might be a useful antibiotic for therapy of eye infections caused by Pseudomonas aeruginosa