To compare epirubicin, cisplatin, and capecitabine (ECX) with fluorouracil, leucovorin, and irinotecan (FOLFIRI) as first-line treatments in patients with advanced gastric or esophagogastric junction (EGJ) adenocarcinoma. This open, randomized, phase III study was carried out in 71 centers. Patients with locally advanced or metastatic gastric or EGJ cancer were randomly assigned to receive either ECX as first-line treatment (ECX arm) or FOLFIRI (FOLFIRI arm). Second-line treatment was predefined (FOLFIRI for the ECX arm and ECX for the FOLFIRI arm). The primary criterion was time-to-treatment failure (TTF) of the first-line therapy. Secondary criteria were progression-free survival (PFS), overall survival (OS), toxicity, and quality of life. In all, 416 patients were included (median age, 61.4 years; 74% male). After a median follow-up of 31 months, median TTF was significantly longer with FOLFIRI than with ECX (5.1 v 4.2 months; P = .008). There was no significant difference between the two groups in median PFS (5.3 v 5.8 months; P = .96), median OS (9.5 v 9.7 months; P = .95), or response rate (39.2% v 37.8%). First-line FOLFIRI was better tolerated (overall rate of grade 3 to 4 toxicity, 69% v 84%; P < .001; hematologic adverse events AEs, 38% v 64.5%; P < .001; nonhematologic AEs: 53% v 53.5%; P = .81). FOLFIRI as first-line treatment for advanced gastric and EGJ cancer demonstrated significantly better TTF than did ECX. Other outcome results indicate that FOLFIRI is an acceptable first-line regimen in this setting and should be explored as a backbone regimen for targeted agents.