['To examine peroxisome proliferator-activated receptor gamma (PPARgamma) mRNA expression quantitatively in human renal cell carcinoma (RCC) cell lines and RCC tissue, as well as in corresponding normal kidney tissue.', 'We examined PPARgamma mRNA expression quantitatively in six human RCC cell lines by real-time reverse transcription-polymerase chain reaction. In addition, we evaluated the relationship between cell growth inhibition by PPARgamma ligands and the level of PPARgamma mRNA expression. We compared the expression of PPARgamma mRNA in 47 RCC tissues with that in corresponding normal kidney tissue, and investigated the relationship between clinicopathological features and the level of PPARgamma mRNA expression.', 'Among the six RCC cell lines, five showed decreased PPARgamma mRNA expression. There was no relationship between the inhibitory effects of PPARgamma ligands and PPARgamma mRNA expression levels. Of the tissues from 47 RCC patients, 25 (53%) showed decreased expression of PPARgamma mRNA compared to corresponding normal kidney tissue, and one was equivalent to normal tissue. These patients had distant metastasis at diagnosis more frequently than the remaining patients with high expression. There was also a trend for these patients to have a higher stage.'] Is peroxisome proliferator-activated receptor gamma frequently underexpressed in renal cell carcinoma?