Stomach cancer incidence rates vary by ethnic group in New Mexico, with American Indians and Hispanic Whites at higher risk than the state's non-Hispanic White population. To further characterize the descriptive epidemiology of this disease in New Mexico, we investigated temporal trends in stomach cancer mortality and incidence rates. Stomach cancer mortality rates declined over a 25-year period (1958-1982) among New Mexico's Hispanic and non-Hispanic Whites. Birth cohort analysis suggests that much of the decline was achieved prior to 1968. Stomach cancer mortality rates did not drop among American Indians during the same period. Stomach cancer incidence rates remained constant for Hispanic Whites, non-Hispanic Whites, and American Indian males over a 13-year period (1969-1982), but more than doubled among American Indian females. Although environmental factors have been implicated in the etiology of stomach cancer, little is currently known about the distribution of such risk factors among the ethnic groups described in this report. The environmental and biological correlates of sex, ethnicity, and socioeconomic status that determine stomach cancer risk merit further investigation in New Mexico.