p53 gene mutation (exon4, 5, 6, 7, 8 and intron6) in gastric cancer and precancerous lesions and p53 gene (exon4 and ontron6), APC gene deletion in gastric carcinomas were studied by PCR/SSCP and PCR/RFLP- Results showed mutation rate of p53 in metaplasia, dysplasia and gastric carcinoma was 37. 5 % (3/8), 42. 11 % (8/19), 53. 33 (16/30) respectively- There was significant dif-ference among groups of metaplasia, dysplasia, cancer and normal controls. Noexon8 mutation was found in metaplasia and dysplasia, but 4 cases were found to have exon8 mutation in cancer group. It is suggested that exon8 mutation occurs at the late stage of gastric cancer, but exon 5, 6, 7 mutation occur in the course ofprecancerous lesion to cancer. Loss of heterozygosity (LOH) of exon4, intron6,APC was 47,37 % (9/19), 8. 73% (2/23), 16. 67 % (3/18) respectively. LOH of exon4 had something to do with poor differentiation, lymph node metastasis,depth of invasion- LOH of exon4 may be one of prognostic marker of gastric cancer. We are led to conclude that p53 gene mutation is an early event and perhaps work together with ras oncogene in gastric carcinogenesis p53 gene mutation (exon4, 5, 6, 7, 8 and intron 6) in gastric cancer and precancerous lesions and p53 gene (exon4 and ontron 6), APC gene deletion in gastric carcinomas were studied by PCR / SSCP and PCR / RFLP- mutation rate of p53 in metaplasia, dysplasia and gastric carcinoma was 37.5% (3/8), 42. 11% (8/19), 53. 33 (16/30) respectively- There was significant dif-ference among groups of metaplasia, dysplasia, cancer and normal controls. Noexon8 mutation was found in metaplasia and dysplasia, but 4 cases were found to have exon8 mutation in cancer group. It is suggested that exon8 mutation occurs at the late stage of gastric cancer, but exon 5 , 6, 7 mutation occurred in the course of precancerous lesion to cancer. Loss of heterozygosity (LOH) of exon 4, intron 6, APC was 47, 37% (9/19), 8. 73% (2/23) % (3/18) respectively. LOH of exon 4 had something to do with poor differentiation, lymph node metastasis, depth of invasion-LOH of exon 4 may one of the prognostic markers of ga We are led to conclude that p53 gene mutation is an early event and perhaps work together with ras oncogene in gastric carcinogenesis