context: gastrointestinal stromal tumor (gist) is the most common mesenchymal tumor. cellular proliferation and apoptosis is gaining importance for predicting prognosis in several cancers. objective: to investigate the ki67 and p53 immunostaining in gists. methods: specimens from 40 patients with gist were assessed for immunohistochemical expression of ki67 and p53. the tumors were divided according the risk of recurrence in two groups: i with high or intermediate risk and; ii with low or very low risk. results: among the 40 patients, 21 were men, the mean age was 56 years, 16 occurred in the small intestine and 13 in the stomach, 5 in the retroperitonium, 4 in the colon or rectum and 2 in the mesenterium. thirty two tumors were from group i and 8 from group ii. half of the patients developed recurrence, being 90% of the group i (p = 0.114). the tumor ki67 labelling index ranged from 0.02 to 0.35 (mean level 0.12). this index was marginally higher in the group i patients with recurrence (p = 0.09) compared to the patients of the same group without recurrence. p53 staining was expressed in 65% of the gists. a higher frequency of p53 and ki67 had been found in the group i tumors when compared to the other group (p = 0.022; or = 8.00 - ic 95%: 1.32-48.65). conclusion: the most common site was the small intestine and 80% had a malignant potential justifying the high recurrence observed. no significant correlation was found between p53 and overall outcome of the patients. in group i patients, the evaluation ki67li may be a marker of prognosis. the positivity of both markers is higher among the patients with worst prognosis than in the others.