Epidemiologic data on local complications after breast augmentation are scarce. In particular, few prospectively collected data are available on modern breast implants on this issue. Using data from the Danish Registry for Plastic Surgery of the Breast, the authors examined determinants of surgery-requiring complications and capsular contracture grades III to IV among 2277 women who underwent cosmetic breast implantation from June 1999 through April 2003. During an average follow-up period of 1.6 years after implantation, 4.3% of these women (3% of implants) required secondary surgery as a result of short-term complications. The most frequent clinical indications for surgery were displacement of the implant (38%), capsular contracture grades III to IV (16%), ptosis (13%), and hematoma (11%). Overall, the authors found that inframammary incision and subglandular placement were associated with decreased risks of developing complications requiring surgical intervention, whereas implants larger than 350 mL increased the risk of such complications (relative risk [RR], 2.3; 95% confidence interval [CI], 1.3-4.0). Thirty-nine Baker III to IV capsular contractures were identified, of which 22 were treated surgically within the study period. Submuscular placement of the implant decreased the risk of capsular contracture grades III to IV (RR, 0.3; 95% CI, 0.2-0.8), whereas surgical routes other than inframammary and drainage of implant cavity were associated with increased risk of capsular contracture. Current surgical practices and modern implants used for breast augmentation produce fewer short-term complications than procedures and devices of the past. This prospective study indicates that surgical procedures are more important predictors for local (short-term) complications than implant or patient characteristics.