Objective 　To determine the incidence and risk factors of postoperative residual curarization (PORC) in patients with breast cancer after total intravenous anesthesia (TIVA) with vecuronium. Methods 　Two hundred and fifty-seven female patients with breast cancer undergoing breast-cancer surgery were enrolled into the present study. Anesthesia was induced with target-controlled infusion of propofol (Cp 3-4μg/ml) and remifentanil (2-3 ng/ml). A bolus of vecuronium 0.1mg/ kg was administered intravenously over 5-10s as soon as the patient lost consciousness, and laryngeal mask was placed 3min later. Mechanical ventilation and TIVA were performed for maintaining anesthesia and keeping bispectral index (BIS) between 40 to 60 during the operation. According to the duration of operation, 0.02mg/kg of vecuronium was administrated intermittently. Extubation of the laryngeal tube was performed according to clinical criteria. Train-of-four ratios (TOFr) were immediately measured with Veryark-TOF (Guangzhou Weilifangzhou Technology Ltd, China) in the recovery room. The patients were divided into two groups (Group N and Group R) according to the value of TOFr at the time of extubation. N denoted the non-residual neuromuscular blockade group (TOF≥0.7), and R denoted the residual neuromuscular blockade group (TOF<0.7). Results 　The incidence of PORC was 60.3% among 257 patients. There was no significant difference of BMI and duration of anesthesia between groups (P>0.05). In group R, age and hemoglobin level were lower (P<0.05 ), but the incident of anemia was same between groups (32.4% vs. 40.6%, P>0.05). More patients in Group R received neoadjuvant chemotherapy and multiple boluses of vecuronium administration, and the duration between last dose of vecuronium to extubation was also prolonged compared with Group N (P<0.05). Multivariate logistic regression analysis identified that age, neoadjuvant chemotherapy and multiple boluses of vecuronium administration were not associated with increased risk of PORC. Duration from last dose of vecuronium to extubation was associated with increased risk of PORC (OR=0.970, 95%CI 0.956-0.984, P<0.001). Conclusions　PORC is commonly used in patients with breast cancer. Duration from last dose of vecuronium to extubation is associated with increased risk of PORC. DOI: 10.11855/j.issn.0577-7402.2016.03.14