14-3-3 Sigma is a checkpoint control gene that promotes G2 arrest following DNA damage. The inactivation of the 14-3-3 sigma gene, primarily by methylation-mediated silencing, has been reported in various human cancers. The loss of 14-3-3 sigma expression may contribute to malignant transformation by impairing the G2/M cell cycle checkpoint function, allowing an accumulation of genetic defects. In this report, we measured 14-3-3 sigma expression in 34 gastric and 35 colorectal cancers by using semi-quantitative reverse transcription-polymerase chain reaction and Western blot analysis. We also analyzed the association between 14-3-3 sigma expression and clinicopathological parameters including p53 status. Semi-quantitative reverse transcription-polymerase chain reaction and Western blot analysis showed that 14-3-3 sigma was significantly overexpressed in gastric and colorectal cancer tissues compared with normal ones (P<0.01). The immunoreactive 14-3-3 sigma protein was mainly detected in cytoplasm of cancer cells. Sigma overexpression tended to be associated with lymph node metastasis (P=0.08) in colorectal cancer. There was significant correlation between 14-3-3 sigma protein expression and the Ki-67 labeling index in gastric cancer (P=0.001). No significant association was observed between 14-3-3 sigma expression and p53 status. These results suggest that overexpressed 14-3-3 sigma in cancer cells might be induced by the p53 independent pathway, and that increased 14-3-3 sigma expression could contribute to cancer cell proliferation and the development and/or progression of human gastrointestinal cancers.