We studied DNA copy number changes in gastric cancer (GC) using comparative genomic hybridization (CGH) analysis on 35 resected gastric carcinomas (22 of the intestinal type and 13 of the diffuse type). Eighty-three percent of the cases showed DNA copy number changes. Gains were more common than losses (median of 3 and 1 in primary tumors of the intestinal and diffuse type, respectively). The most common gains were detected on 20q [46%; 12 intestinal type (55%) and four diffuse type (31%)], 8q [37%; 10 intestinal type (45%) and three diffuse type (23%)], and 17q12-21 [29%; all but one intestinal type (41%)]. The most frequent losses were detected on 18q [26%; all intestinal type (41%)] and on 4q [23%; all intestinal type (32%)]. High-level amplifications were observed in the intestinal type of tumors at 17q12-21 (three tumors), 20q (three tumors). 2q (one tumor), and 18q (one tumor). In the diffuse type, high-level amplification was detected once at 13q.