No prospective phase III trials have directly compared the efficacy of pemetrexed plus cisplatin (Pem-Cis) with docetaxel plus cisplatin (Doc-Cis) in nonsquamous non–small-cell lung cancer. A total of 148 chemotherapy-naive patients lacking driver mutations were randomized to the Pem-Cis or Doc-Cis arm. The progression-free survival and response rate was similar between the 2 arms, although adverse events and more severe toxicities were observed more frequently in the Doc-Cis arm. To date, no prospective phase III trials have directly compared the efficacy of pemetrexed plus cisplatin (Pem-Cis) with docetaxel plus cisplatin (Doc-Cis) in patients with nonsquamous non–small-cell lung cancer. A total of 148 chemotherapy-naive patients lacking driver mutations were randomized into 21-day regimens of cisplatin 70 mg/m2 with either docetaxel 60 mg/m2 (n = 71) or pemetrexed 500 mg/m2 (n = 77) for ≤ 4 cycles. The primary objective was to assess the noninferiority of progression-free survival (PFS) for patients receiving the Doc-Cis regimen. The secondary endpoints were the response rates, overall survival, and toxicity profiles. Partial remission was observed in 24 (31.2%) and 24 (33.8%) patients in the Pem-Cis and Doc-Cis groups, respectively. The median PFS was 4.7 months (95% confidence interval CI, 4.4-5.0) in the Pem-Cis arm and 4.4 months (95% CI, 3.7-5.1) in the Doc-Cis arm (P > .05). The median overall survival was longer in the Doc-Cis arm (13.3 months; 95% CI, 8.1-18.5) than in the Pem-Cis arm (11.7 months; 95% CI, 8.6-14.8; P > .05). Between the 2 arms, no significant difference was found in the subsequent treatments after failure of first-line treatment. The rate of grade 3 or 4 neutropenia and febrile neutropenia was greater in the Doc-Cis arm than in the Pem-Cis arm. In nonsquamous non–small-cell lung cancer patients lacking driver mutations, the PFS and response rates were similar between the 2 arms, and toxicity was tolerable, although adverse events and more severe toxicities were observed more frequently in the Doc-Cis arm.