Introduction: Capture-recapture methods have been suggested for reducing costs of disease registration as well as reducing bias in incidence estimations. This study aimed to estimate the gastric cancer incidence in theTehran metropolis population during 2002-2006. Materials and Methods: We investigated new cases of gastric cancer reported by three sources; death certificates, pathology reports, and medical records to Tehran population-based cancer registry during 2002-2006. G 2 statistics and the two-source capture-recapture method were used to select the best-fitted log-linear model and to estimate incidence, respectively. EXCEL software version 2007 and SPSS software version 16 were used for this research. Results: The number of reported cases was 4,463, with an average age of 68.5 (±12.9) years. We found the model that combined two sources of data including pathology reports and medical records and furthermore complemented by death certificates as the best model. The reported and the estimated incidences were 11.0 and 27.1 per 100,000 respectively. Conclusions: The incidence estimated by twosource capture-recapture method is about three times higher than the incidence reported by the sources under investigation. It is recommended to move towards the implementation of population-based cancer registration using various sources of data collection to achieve more accurate data. , Alireza Mosavi-Jarrahi 4 * special events. Such information is very important for policymakers and health workers (Hook and Regal, 1995; IWGDMF, 1995). Using capture-recapture methods is recommended for reducing the costs of disease registration as well as reducing bias in incidence estimations and for comparing population subgroups. Modeling the effect of intervening variables presents better estimations of population size and therefore solves many problems of the estimation of population size (Tilling, 2001).Tehran population-based cancer registry center has started since 1998. The main goal of this center is to measure cancer incidence in Tehran metropolis. Since Tehran is a referral center for all around the country, epidemiologists and experts of this center faced with the large amounts of data encountering many problems. Data collection area of this center includes Tehran metropolis plus Islamshahr and shemiranat townships (Mohagheghi et al., 2009;Aghaei et al., 2012; Haidari et al., 2012).Central areas of Iran including Tehran have the highest incidence of gastric cancer after North and Northeast regions (Kolahdoozan et al., 2010 (Mohagheghi et al., 2009). This study aims to estimate the real incidence of gastric cancer in the Tehran population. Materials and MethodsNew cases of gastric cancer that have been reported by three sources including death certificates, pathology reports, and medical records to Tehran Metropolitan Area cancer registry center during 2002-2006 years. Since Tehran is a referral center, cases not being among the areas covered by the registration center (Tehran, Islamshahr and Shemiranat townships) a...