Background: Harvesting lymph node (LN) after gastrectomy is essential for accurate staging. Conventional method (CONV) to retrieve LN immediately after surgery is accepted in Japan but its efficacy and quality highly depends on the case and examiners. Another method is to retrieve LN stained by methylene blue dye (MBD), by which the physicians may easily pick up blue LN. This trial evaluated the efficiency and quality of both methods in randomized fashion. Methods: Key eligible criteria are as follows. (i) Histologically proven adenocarcinoma of the stomach, (ii) Clinical stage I-III, (iii) R0 resection is planned by gastrectomy with D1+ or D2 lymphadenectomy. Examiners for harvesting LN are qualified based on the experience. After curative surgery, LNs are harvested from the specimen immediately after surgery in the CONV group and from the specimens who had been fixed with 10% buffered formalin with methylene blue for 48 hours in the MBD group. The primary endpoint is the ratio of the pathological number of the harvested LNs per time (minutes) as an efficacy measure. The secondary endpoint is the pathological number of harvested LNs as a quality measure. The sample size was determined to be 60 considering the primary measurement as 40 LNs / 30 minutes in CONV and 40 LNs / 22.5 minutes in MBD with two-sided alpha error of 5% and statistical power of 80%. Results: Between August 2012 and December 2012, 60 patients were assigned to CONV (n=29) and MBD (n=31). Total/subtotal gastrectomy was 12/17 in CONV and 12/19 in MBD, respectively. D1+/D2 was 17/12 in CONV and 15/16 in MBD, respectively. Baseline demographics were well balanced between the both. The number of pathological harvesting LNs (median, range) was 32 (11-57) in CONV and 41 (17-79) in MBD (P=0.005). The time per case for harvesting LN (median, range) was 33 (15-58) minutes in CONV and 25 (13-102) minutes in MBD (p=0.743). The ratio of the number of the harvested LNs per time (median, range) was 1.12 (0.42-2.07) in CONV and 1.42 (0.50-3.07) in MBD (p=0.01). Conclusions: When harvesting LN in gastric cancer surgery, methylene blue dye-assisted technique is superior in the efficacy and quality as compared with conventional method. Clinical trial information: UMIN000008624.