We examined the incidence of non-Hodgkin's lymphoma (NHL) in Chinese, Japanese, and Filipino residents of the United States to obtain further clues about the etiology of the disease. The age, race, and birthplace of residents of Hawaii, San Francisco/Oakland (California), and western Washington who had received a diagnosis of NHL during the period 1973-86 were obtained from population-based cancer registries, and a special tabulation from the 1980 Census was used to estimate the number of person-years at risk for each category of resident. The incidence of NHL in each of the Asian groups examined was 35 to 85 percent that of US-born Whites. However, there was no consistent trend of increasing incidence with increasing generation of residence in any of the groups. In Asian-Americans, the risk of small cell lymphocytic and plasmacytoid lymphoma was 10 to 85 percent that of Whites, although no clear trends of risk with generation of residence in the US were observed. They also were at a reduced risk of follicular lymphoma, and in Chinese and Japanese persons, the risk was lower in first generation than in later generation migrants (Chinese: Asian-born relative risk [RR] = 0.11, US-born, RR = 0.84; Japanese: Asian-born, RR = 0.15, US-born, RR = 0.36). The risk of diffuse lymphoma was similar in Chinese- and Japanese-Americans and US-born Whites. We conclude that, with the exception of follicular lymphoma, the basis for the relatively low incidence of NHL in Asian-Americans does not lie in exposures or characteristics that differ between the migrants themselves and their descendants.