105 patients admitted for cataract surgery were treated pre-operatively with polyvinylpyrrolidone-iodine (PVP-I) as a disinfectant, and consecutive bacterial cultures were obtained before initiating surgery and at the end of the operation. A control group (n = 99) only had a standard disinfection procedure of the eye (including instillation of Terramycin cum polymyxin B cream in the conjunctival sac the evening before surgery). The cultures obtained from the conjunctival sac of the control group principally showed growth of Staph. albus and Staph. aureus, and to a minor degree diphtheroids (Corynebacterium species). Proteus mirabilis, Escherichia coli and micrococci. There was a significant quantitative diminished growth (P less than 0.05) of bacteria in the group of patients treated with PVP-I compared to the control group. Concerning the growth of Staph. albus, this was reduced to almost one third and other bacteria were almost eliminated in the group receiving PVP-I. As we disclosed no toxic or allergic reaction post-operatively which could be related to the use of PVP-I as a disinfectant, this agent seems to constitute an effective pre-operative antimicrobial treatment, taking into consideration the broad antimicrobial spectrum of PVP-I shown by other authors.