Concern has been raised recently regarding the absence of information on the occurrence and severity of local complications after cosmetic breast implantation. The authors evaluated the occurrence of local complications in a large epidemiological retrospective cohort study of women with cosmetic breast implants in Denmark. All women with breast implants were identified from the files of two private clinics of plastic surgery in Denmark. Information on implant characteristics, surgical procedure, as well as short- and long-term complications was obtained through medical record review. Patient characteristics were obtained through a self-administered questionnaire. A total of 754 women (1,572 implants) had at least one cosmetic implantation performed at the study clinics. Average age at implantation was 32 years. Implant types included silicone double lumen with textured surface, 31.2%; silicone single lumen with textured surface, 27.8%; silicone single lumen with smooth surface, 24.5%; silicone double lumen with smooth surface, 0.8%; and other or missing information, 15.7%. Average implant size was 247 ml (range, 110-630 ml). Placement was submuscular for 91.3% of implants, subglandular for 2.6%, and 6.1% had no available information. Overall, 77.8% of implantations were not followed by complications, 17.8% were followed by one complication, 3.6% were followed by two complications, and 0.8% were followed by three or more complications. In 94.6% of implantations, no additional hospitalizations were recorded as a result of complications. Forty-seven of 57 explantations/reimplantations were secondary to postoperative complications. General complications such as hematoma and infection were rare, occurring in 2.3% and 2.0% of implantations respectively. Capsular contracture remains the most common complication, occurring in 11.4% of implantations. In this investigation, among the first epidemiological studies of local complications, the authors found cosmetic breast implant surgery to be associated with a low frequency of normal surgical complications such as infection, hematoma, and wound dehiscence. Most complications were mild and did not lead to additional hospitalization. The complication that led most frequently to the need for additional surgery/hospitalization was capsular contracture. Kjøller K, Hölmich LR, Jacobsen PH, Friis S, Fryzek J, McLaughlin JK, Lipworth L, Henriksen TF, Jørgensen S, Bittmann S, Olsen JH. Epidemiological investigation of local complications after cosmetic breast implant surgery in Denmark.