Background: The proportion between metastatic and examined lymph nodes (N ratio) has been proposed as an independent prognostic factor in gastric cancer (GC) patients. The aim of this study is to investigate the relationship between the metastatic N ratio and the prognosis of GC after curative D2 surgery Methods: We retrospectively reviewed the data of 458 ARTIST patients who underwent D2 gastrectomy followed by adjuvant chemotherapy with capecitabine plus cisplatin (XP, n = 228) or chemoradiotherapy (XPRT, n = 230). Disease-free survival (DFS) of the patients was analyzed in order to evaluate the influence of N ratio on treatment outcome. Four N ratio categories (0% v 1-9% v 10-25% v > 25%) were employed, and statistical analysis was performed using adjusted Cox regression and stratified survival analysis. Results: Among 458 GC patients enrolled in ARTIST, the proportion of patients with at least 15 lymph nodes examined was 99%. As expected, there was a significant interaction between the N staging and N ratio. At multivariate analysis, N ratio was retained as an independent prognostic factor for DFS: HR for N ratio 0%, 1; N ratio 1-9%, 1.061; N ratio 10-25%, 1.202; and N ratio > 25%, 3.571. Furthermore, there also was a significant difference in DFS between XPRT and XP arms for patients with higher N ratio. In patients with N ratio > 25%, the 5-year DFS was 55% v 28% for XPRT and XP arms, respectively (HR, 0.527; 95% CI, 0.307 to 0.904; P = 0.020). Conclusions: In patients with curatively resected GC, N ratio is independently associated with DFS. Although this finding warrants further investigation in prospective studies, benefit with chemoradiotherapy in D2 resected GC seems to be limited to those with N ratio > 25% Clinical trial information: NCT00323830