Abstract： S:Background Seroma formation is one of the most common complications after breast cancer surgery. Various risk factors have been evaluated for their associations with the development of seromas in Western populations. However,similar data are not available in Chinese series. Therefore, we sought to investigate the potential risk factors for Chinese breast cancer patients.Methods A prospective study of female breast cancer patients undergoing surgery was carried out in Cancer Hospital of Fudan Unversity, Shanghai, China. Univariate analyses were performed by chi-square test or Student's t test or Mann-Whitney test and multivariate analyses by stepwise Logistic regression. The logistic model included age (years),total serum protein concentration (g/L), drainage volume on postoperative day 3 (POD 3; ml) and time to daily drainage volume not more than 30 ml (TTV30; days).Results A total of 158 patients with breast cancer were studied. The mean age at diagnosis was (52.14±10.77) years (range 25-92). During the follow-up period, 24 (15.2%) patients developed seromas. Calculated as continuous variables in the stepwise Logistic regression, age (OR=1.090, 95% CI 1.028-1.155, P=0.004), total serum protein concentration (OR=0.886, 95% Cl 0.791-0.992, P=0.036), drainage volume on POD3 (OR=1.013, 95% CI 1.002-1.023, P=0.017) and TTV30 (OR=1.273, 95% CI 1.039-1.561, P=0.020) were independent risk factors for seroma formation. Additionally,significant difference in daily drainage volume was substantiated in the analysis by seroma formation (P=0.034) rather than by type of surgery (P=0.713).Conclusions Although the pathogenesis of seroma remains controversial, such risk factors as age, nutritional status,drainage volume on POD3 and TTV30 should be considered for prediction and prevention of seroma formation in Chinese breast cancer patients.