Abstract: Objective To study the expression of Smo protein and the downstream transcription factor Gli1 protein in Sonic hedgehog signal transduction pathway in gastric carcinoma.Methods A tissue microarray was constructed using 85 gastric carcinoma and 25 normal gastric mucosa specimens.The expression of Smo and Gli1 proteins were detected immunohistochemically and the correlation between their expression in gastric carcinoma was analyzed.Results Only weak expression,if any,of Smo and Gli1 proteins was detected in normal gastric mucosa,but in papillary adenocarcinoma,tubular adenocarcinoma and poorly differentiated adenocarcinoma,their expressions were significant increased as the differentiation degree was lowered.Smo protein expression in gastric carcinoma was significantly correlated with that of Gli1 protein with correlation coefficient of 0.989(P<0.001).Conclusions The abnormal activity of Sonic hedgehog signal transduction pathway may play an important role in the occurrence of papillary adenocarcinoma,tubular adenocarcinoma and poorly differentiated adenocarcinoma,and this abnormality is associated with Smo protein overexpression,which upregulates the expression of the downstream transcription factor Gli1 protein.