['Preoperative chemotherapy is frequently given to shrink or decrease the chance of metastasis. However, chemotherapy has well-recognized side effects that may complicate the perioperative period. We therefore tested the hypotheses that chemotherapy within 30 days before cancer surgery is associated with an increased risk of mortality and with a composite of major morbidities within 30 postoperative days.', 'We evaluated 971,455 patients from the American College of Surgeons National Surgical Quality Improvement Program database. Patients were defined as having chemotherapy when they were given any chemotherapy for malignancy within 30 days before surgery. We successfully matched 1,348 pairs of chemotherapy recipients and non-recipients.', 'Twenty-one of the 1,348 (1.6%) non-chemotherapy patients died within 30 days after surgery compared with 30 of the 1,348 (2.2%) chemotherapy patients. The odds of mortality were not statistically different between groups based on our logistic regression model [odds ratio (OR) = 1.47; 95% confidence interval (CI) 0.82 to 2.64; P = 0.19]. The most common complication observed was wound infection in 13.1% of non-chemotherapy patients compared with 14.2% of the chemotherapy patients. There was similarly no difference between groups for the collapsed composite of major morbidities [OR = 1.17; 95% CI 0.97 to 1.42; P = 0.09].'] Does chemotherapy within 30 days before surgery augment postoperative mortality and morbidity?