Objective: To study the anterior chamber contamination during non-complicated cataract surgery and its relationship with normal conjuctival organisms. Setting: Ophthalmology Department, La Fe Hospital, University of Valencia. Patients: Forty patients who had undergone cataract extraction using either ECCE, phacoemulsification or nucleus fracture methods. Results: Positive cultures of aqueous humour were obtained in 32.5% of cases. The most commonly isolated organism was Staphylococcus coagulase-negative. Only in 7.7% of cases was the microorganism found in the conjunctiva the same as that found in the anterior chamber. The inoculum size ranged between 20 and 160 colonies/ml. One of the cases studied developed endophthalmitis 36 hours after surgery. Conclusions: The conjunctiva could not be the main source of anterior chamber contamination during surgery, although it would be capable of contributing a small number of inocula of organisms without causing any complications.