We previously found that half-strength (5%) povidone-iodine solution significantly reduced the bacterial flora of the conjunctiva. To compare the antibacterial effect of a topical combination antibiotic (Neosporin ophthalmic solution) given three times daily for three days preoperatively with that of half-strength povidone-iodine solution given as part of the preoperative preparation, conjunctival cultures were studied from 35 patients undergoing ocular surgery. When used individually, the antibiotic and povidone-iodine solutions caused a similar and substantial decrease in the number of colonies and species of bacteria cultured. When both drugs were used together, the decrease was even more striking, making 83% of the conjunctivae sterile. To minimize bacterial flora before ocular surgery, we recommend that a broad-spectrum topical antibiotic be given for three days preoperatively and that half-strength povidone-iodine solution be used as part of the preoperative preparation.