Among all tumours diagnosed worldwide, gastric adenocarcinoma is the second most frequent type of malignancy. In Brazil, it is estimated to be the fifth most frequent type of neoplasia. According to the classification of Laurén, these tumours are divided into well differentiated and ill differentiated gastric adenocarcinomas. There are studies suggesting that the first type develops through remodulation of genes involved in the suppressor pathway and the second through remodulation of genes belonging to the mutational pathway. The gene PTEN is located in region 10q23 and is altered in several human tumours. In gastric cancer, this gene is thought to take part in the suppressor pathway. In our study, DNA was obtained from 48 gastric adenocarcinoma samples, amplified, screened for all exons of the PTEN gene by PCR-SSCP and then confirmed by sequencing. There was only one sample that presented an alteration and that was a transversion. Our results corroborate the hypothesis that somatic alterations in the PTEN gene are rare events in gastric cancer.