Background/Aims: Wide-type Adenomatous polyposis coli (APC) gene binds to β-catenin and APC mutants lead to cytosolic accumulation of β-catenin which serves as a component of carcinogenesis. We investigated the relationship between loss of heperozygosity (LOH) of APC gene and β-catenin expression in gastric cancer. Methods: We examined the LOH of exon 11 of APC gene in frozen specimens of 28 gastric adenocarcinomas and 28 normal gastric tissues obtained from the same patient using polymerase chain reaction and restriction fragment length polymorphism. The cytoplasmic and nuclear β-catenin were investigated by Western blotting. Results: The heterozygosity of APC gene was observed in 21% (6/28), and LOH of APC gene was observed in 33% (2/6). In 14% (4/28) of gastric cancers, β-catenin was strongly expressed both in the cytoplasm and the nucleus. The LOH of APC gene was not correlated with accumulation of β-catenin. Conclusions: The LOH of exon 11 of APC gene is not correlated with an increase of β-catenin in gastric cancer. The cytoplasmic accumulation of β-catenin may be associated with mutations in APC-β-catenin-Tcf-4 pathway. (Kor J Gastroenterol 2000;35:724 - 731)