In a prospective, random, double-blind, and concurrently controlled clinical study of 124 patients having augmentation mammaplasty, using multiple independent subjective judges as well as objective compressibility measurements, the use of a variety of local antibacterials in or around inflatable retromammary prosthetic implants reduced the early postoperative onset of class III to IV capsular contracture by sevenfold (85 percent) and the final incidence by more than half (50 percent) (p less than 0.01). We believe this study provides the most unequivocal evidence to date that the cause of capsular contracture in retromammary augmentation is periprosthetic bacterial contamination. Irrigation with a 5 percent povidone-iodine (50 percent Betadine) solution was as effective as other techniques and is currently our procedure of choice.