We investigated the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and the role of PPARgamma in cell growth in human gastric cancer cells. Reverse transcription-polymerase chain reaction, Northern blot and Western blot analyses showed that a human gastric cancer cell line, MKN45, expressed PPARgamma mRNA and protein. Luciferase assay in MKN45 cells showed that troglitazone, a selective ligand for PPARgamma, transactivated the transcription of a peroxisome proliferator response element-driven promoter. Troglitazone or pioglitazone, selective ligands for PPARgamma, inhibited the growth of MKN45 cells in a dose-dependent manner. Co-incubation of MKN45 cells with troglitazone induced DNA ladder formation. These results suggest that human gastric cancer cells express PPARgamma and that activation of PPARgamma inhibits cell growth and induces apoptosis in gastric cancer cells.