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Background and Objective: Cancer is third cause of mortality and morbidity in Iran, after heart diseases and car accidents. This study was aimed to determine the incidence rate gastrointestinal tract cancer during 1998-2001 in Tehran, Iran. Materials and Methods: In this descriptive study, the whole population residing in areas of Tehran, Shemiranat and Eslam'shahr area were supposed to be as the population in risk. Data of cancer recordings were collected from pathology and medical records archives. Those with ICD-10-based diagnosed cancer during 1998-2001, who have been inhabited in above area for at least 1 year, were supposed as canceric cases. The incidence rate of various kinds of cancer were adapted based on age-structure of world population and were calculated by dividing the total rate of this period to 4 in an annual manner. Results: The annual age-specific standardized incidence rate of gastric cancer in men and women were 12.9 and 5.8 per 100000, respectively. The row incidence rate in men and women were 9.2 and 4.1, respectively. Ealderly age groups of both men and women had higher incidence rate of gastric cancer. The annual age-specific standardized incidence rate of colon cancer in men and women were 5.7 and 5.4 per 100000, with row incidence rate of 4.3 and 4.0 per 100000, respectively. The annual age-specific standardized incidence rate of esophageal cancer in men and women were determined as 5.1 and 3.9 per 100000, with row incidence rate of 3.7 and 2.7 per 100,000, respectively. Conclusion: This study showed that gastric cancer is the most common type of gastrointestinal cancers in Tehran. Therefore it is suggested the related risk factors in this area should be determined.