The time trend in incidence of stomach cancer in males and females in Mumbai, India during 1988 to 1999 was estimated using data collected by the Bombay Population-based Cancer Registry. During the 12-year period, a total of 3657 stomach cancer cases (3.9% of all cancers) were registered by the Bombay Population-based Cancer Registry of which 2467 (5.1% of all male cancers) were in males and 1184 (2.6% of all female cancers) in females. For evaluation of the trend, we applied a linear regression model based on the logarithm of the observed incidence rates. The annual percentage changes were also computed for the incidence rates for evaluating the time trend. A statistically significant decreasing trend in the overall age-adjusted incidence rates of stomach cancer was observed during the period 1988 to 1999, with an yearly decrease of 4.44% in males and 2.56% in females. This decrease was most striking in males in the age groups 40-59 and 60+, and in females only in the age group 40-59. The probability estimates indicated that one out of every 92 men and one out of every 187 women will contract a stomach cancer at some time in their whole life and 95% of the chance is after his or her 40th birthday. The decreasing trend in the age-adjusted incidence rates of stomach cancer in both the sexes indicates that there is a critical change in the etiology of this cancer. The findings may provide clues relating to various life-style and environmental changes impacting on stomach cancer incidence.