We investigated the p53 protein expression in gastrointestinal lymphomas (GIL). Paraffin-embedded samples of 52 patients were examined for this purpose. The avidin-biotin Complex method was used for immunostaining. Nine of the 52 samples (17.3%) showed p53 staining. There was no relationship between the p53 protein expression and clinical characteristics, such as stage, disease localization and tumor burden. Complete remission was higher in patients not expressing this protein, and the p53 protein was more frequently expressed in intermediate and high grade histopathology than low grade lymphomas? but there was no statistically significant difference between the two groups (p = 0.008). Interestingly, patients expressing the p53 protein were younger than the ones not expressing it (30.7 +/- 14.1 vs. 43.6 +/- 15.7 years). We conclude that the p53 protein expression in GILs may be a poor prognostic indicator due to a lower response rate to chemotherapy.