BACKGROUND: There is limited randomized evidence on the comparative outcomes of early-stage lung cancer resection by video-assisted thoracoscopic surgery (VATS) versus open resection. METHODS: We conducted a parallel-group multicenter randomized trial that recruited participants with known or suspected early-stage lung cancer and randomly assigned them to open or VATS resection of their lesions. The primary outcome was physical function at 5 weeks as a measure of recovery using the European Organisation for Research and Treatment of Cancer core health-related quality of life questionnaire (QLQ-C30) (scores range from 0 to 100, with higher scores indicating better function; the clinical minimally important difference for improvement is 5 points). We followed the patients for an additional 47 weeks for other outcomes. RESULTS: A total of 503 participants were randomly assigned (247 to VATS and 256 to open lobectomy). At 5 weeks, median physical function was 73 in the VATS group and 67 in the open surgery group, with a mean difference of 4.65 points (95% confidence interval, 1.69 to 7.61). Of the participants allocated to VATS, 30.7% had serious adverse events after discharge compared with 37.8% of those allocated to open surgery (risk ratio, 0.81 [95% confidence interval, 0.66 to 1.00]). At 52 weeks, there were no differences in cancer progression-free survival (hazard ratio, 0.74 [0.43 to 1.27]) or overall survival (hazard ratio, 0.67 [0.32 to 1.40]). CONCLUSIONS: VATS lobectomy for lung cancer is associated with a better recovery of physical function in the 5 weeks after random assignment compared with open surgery. Long-term oncologic outcomes will require continued follow-up to assess. (Funded by the National Institute for Health Research Health Technology Assessment programme [reference number 13/04/03]; ISRCTN number, ISRCTN13472721.)