The purpose of this study was to evaluate the timewise postoperative respiratory function measured by spirometry and peak flow during the first postoperative week after major emergency abdominal surgery. Patients were tested daily with forced expiratory volume (FEV) and peak flow (PEF) from postoperative day (POD) 1 through to POD7. FEV1, FEV6, FEV1/FEV6 ratio and PEF were analysed by unadjusted linear regression with 95% confidence interval (CI) on mean values for each postoperative day. A total of 35 consecutive patients were included in the study. The FEV at 1 second was 51% of predicted at POD1, which increased to 67% at POD7 (p = 0.005), whereas FEV6 was 55% of predicted at POD1, which increased to 70% at POD7 (p = .008). Respiratory function was not significantly correlated to synchronous pain scores. In conclusion, respiratory function following major emergency abdominal surgery was reduced throughout the first postoperative week irrespective of pain scores.