We compared recent incidence rates for lung cancer in females among several regions in the Pacific Basin, Shanghai, Hong Kong, Miyagi, Hawaii, and Los Angeles, by ethnic group using data from the population-based registry in each area. The rates were high among whites and Hawaiians, intermediate in Chinese, and low in Japanese regardless of area. The risk of lung cancer among females who smoke relative to that in female nonsmokers varied from 1 ethnic group to another as did the proportion of smokers in the populations studied. Most of the interethnic differences in lung cancer incidence rates could be explained by differences in smoking patterns. The estimated annual incidence rate for lung cancer in females after subtraction of the proportion of the incidence due to smoking was 7.5/100,000 population in every ethnic group except the Chinese (15-20/100,000 population). Most of the residual incidences of lung cancer were adenocarcinoma of the lung.