PURPOSE: The purpose of this study was to correlate the immunohistdegrees Chemical expressions of p53, p21 and bcl-2, with their loss of heterozygosity (LOH) and clinical significance. MATERIALS AND METHODS: Paraffin-embedded tissue sections from 30 patients with gastric car cinomas were examined for immunohistdegrees Chemical staining and LOH study. Primary antibodies used in immunohistdegrees Chemical staining were mouse mondegrees Clonal antibody to human p53, p21/ WAF1 and bcl-2. For PCR-LOH assays, D6S271, D6S105, D18S386, TP53, D17S796, and D17S786 microsatellite markers were used. RESULTS: The expression rates of p53, p21 and bcl-2 were 76.7%, 80% and 3.3%, respectively. The expression of p21 was correlated with lymph node metastasis. LOH were found in 20.8% at D6S271, 42.3% at D6S105, 31.6% at D18S386, 39.1% at TP53, 40.9% at D17S796, and 50.0% at D17S786. No correlation was found between the immunohistdegrees Chemical expression and the LOH in these gene sites. CONCLUSION: p53 and p21 were detected in high rate, whereas bcl-2 expression rate was very low in gastric adendegrees Carcinoma. Of them, overexpression of p21 was correlated with the tumor progression. High incidence rate of LOH may play an important role in gastric carcinogenesis. These findings suggest that the effects on apoptosis and cell cycle by p53 and p21 were important in development and progression of gastric cancer.