We aimed to determine predictive factors affecting cosmetic results after breast conserving management in breast cancer. Data on 96 patients with 97 breast cancer cases, who had been admitted to Uludag University M.A. Radiotherapy Center between October 1995 and December 1998 and managed with breast-conserving treatment, were analysed to determine the factors affecting cosmetic outcome, Possible factors affecting cosmesis were grouped as patient-related. tumor-related and treatment-related. Mann-Whitney U test was used in univariate analyses whereas logistic regression was used in multivariate analyses. Median follow-up time was 29.5 months ranging between 11 and 53 months and median age at admission was 50 (range 22-84). Cosmetic results were grouped in five categories; excellent; good; fair; poor and, very poor, using criteria, such as presence of fibrosis, telangiectasia. shape of breast, asymmetry, status of areola, pigmentation. Treated breasts were scored by the patients. three radiation oncologists and a breast surgeon independently. In the analysis performed using scores given by the patients, cases with scores 3 and above (unsatisfactory) were compared with cases with scores below 3 (satisfactory). Eighty-two patients (84%) considered cosmetic result as satisfactory (excellent/good) whereas 15 patients (16%) considered unsatisfactory (fair/poor/very poor). In univariate analysis using Mann Whitney U test, type of surgery (P = 0.0655) was the statistically significant factors affecting cosmetic results. In multivariate analysis using logistic regression, tumor quadrant (P = 0.0060) and elapsed radiation therapy days (P = 0.0090) were the most significant factors. Median values were taken into consideration for the scores given by the physicians and cases with scores 3 and above (unsatisfactory) were compared with cases with scores below 3 (satisfactory). Eighty-two cases were evaluated as satisfactory (84%) whereas 15 cases were unsatisfactory (16%). In this set of data, patient age (P=0.0144), menopausal status (P=0.0111), institution which surgery was performed (P=0.0045), type of surgery (P = 0,0044), placement of metallic clips (P = 0.0083) and skin fibrosis (P = 0.038) were found to be significant in univariate analysis using Mann-Whitney U test. In multivariate analysis using logistic regression, institution where surgery took place (P=0.0015), menopausal status (P=0.0087) and telangiectasia (P=0.0657) were the most significant factors. (C) 2002 Harcourt Publishers Ltd.