Postoperative endophthalmitis remains one of the most devastating complications of eye surgery. In recent years infections with so called ‘nonpathogenic’ organisms like Propionibacterium acnes or coagulase-negative staphylococci have gained in importance. 200 patients were included in this study, from whom preoperative smears of the conjunctiva and intraoperative aspirates of the anterior chamber (at the start and at the end of the operation) had been taken. All samples were investigated for aerobe and anaerobe microorganisms and fungi. 75% of the preoperative smears had been contaminated, with coagulase-negative staphylococci the most commonly isolated bacteria. But, in addition, 28% of the patients had culture-positive anterior chamber aspirates, also with coagulase-negative staphylococci as the most frequent organisms. In all cases inoculum sizes were extremly small (10–20 c.f.u./ml). Probably because of this small inoculum, but also due to the bacteriocidal qualities of the acqueous humor and the integrity of the posterior capsule sac, in no case had postoperative endophthalmitis developed. For the first time, our study tried to correlate the contamination of the anterior chamber aspirate to the used operation technique: first results show that the contamination of the aqueous humor is significantly lower (p < 0.03) if the cataract extraction is performed by phacoemulsification than if done without.