The OAK (Open-Label Anti-PD-L1 Therapy in Advanced Non-Small-Cell Lung Cancer) study is a phase 3, randomised, open-label, multicentre trial comparing atezolizumab and docetaxel in previously treated patients with non-small-cell lung cancer (NSCLC). The primary endpoints were overall survival in the intention-to-treat (ITT) and PD-L1-expression populations. A total of 1225 patients were enrolled, with 425 assigned to each arm. Atezolizumab significantly improved overall survival compared with docetaxel in both the ITT and PD-L1 TC1/2/3 or IC1/2/3 populations. The median overall survival was 13.8 months with atezolizumab and 9.6 months with docetaxel (hazard ratio [HR] 0.73, p=0.0003). Atezolizumab also showed improved overall survival in patients with PD-L1 low or undetectable expression (HR 0.75, p=0.0102). The safety profile of atezolizumab was favourable, with fewer grade 3 or 4 adverse events and immune-mediated events compared with docetaxel. These results support atezolizumab as a new treatment option for previously treated NSCLC, regardless of PD-L1 expression or histology.The OAK (Open-Label Anti-PD-L1 Therapy in Advanced Non-Small-Cell Lung Cancer) study is a phase 3, randomised, open-label, multicentre trial comparing atezolizumab and docetaxel in previously treated patients with non-small-cell lung cancer (NSCLC). The primary endpoints were overall survival in the intention-to-treat (ITT) and PD-L1-expression populations. A total of 1225 patients were enrolled, with 425 assigned to each arm. Atezolizumab significantly improved overall survival compared with docetaxel in both the ITT and PD-L1 TC1/2/3 or IC1/2/3 populations. The median overall survival was 13.8 months with atezolizumab and 9.6 months with docetaxel (hazard ratio [HR] 0.73, p=0.0003). Atezolizumab also showed improved overall survival in patients with PD-L1 low or undetectable expression (HR 0.75, p=0.0102). The safety profile of atezolizumab was favourable, with fewer grade 3 or 4 adverse events and immune-mediated events compared with docetaxel. These results support atezolizumab as a new treatment option for previously treated NSCLC, regardless of PD-L1 expression or histology.