We examined chromosome abnormalities in 4 patients with gastric carcinoma by use of G-banding technique of short-term cultured cells. They were all diagnosed as cases with advanced carcinomas involving subserosa or serosa. Two of them (case 1 & 2) were poorly differentiated adenocarcinomas of which tumor cells were arranged in cords or scattered within lymphoid stroma. Case 3 showed a micro-scopic carcinomatous focus in the mucosa and diffuse tumor permeation in submucosal and subserosal lymphatics. Tumor cells in the lymphatics were pleomorhpic having large vesicular nuclei and prominent nucleoli. Case 4 was mucin producing, well differentiated adenocarcinoma. Chromosomal abnormalities observed were deletion of chromosome 1q, translocation between 16q and 22q and trisomy #12. Karyologic characteristics of two cases were aneuploid carcinomas, tetraploid or hyperdiploid, and the others were within diploid range.