An investigation of time trends and racial patterns in lung cancer risk by histologic type revealed similar time trends for blacks and whites, but excess rates among black men and women for squamous cell carcinoma and among black men for adenocarcinoma. Rates of small-cell carcinoma were similar among blacks and whites. The time trends were consistent with birth cohort effects with peaks in cohort incidence rates for small- cell carcinoma and adenocarcinoma occurring 10 to 20 years after the peak in squamous-cell carcinoma.