The role of tobacco in the etiology of non-Hodgkin's lymphoma (NHL)was evaluated in a combined analysis of data from three population-basedcase-control studies conducted in four midwestern states of the UnitedStates: Nebraska, Iowa, Minnesota, and Kansas. Interviews were obtained from1,177 cases (993 men, 184 women) and 3,625 controls (2,918 men, 707 women )or, if deceased, from their next-of-kin. Overall, there was no associationbetween NHL and tobacco use (odds ratio [OR] = 1.0, 95 percent confidenceinterval [CI] = 0.8-1.1) or cigarette smoking (OR = 1.0, CI = 0.8-1.1). Aslight negative association evident in analyses by intensity and duration ofsmoking was not present when interviews from proxy respondents wereeliminated. There was a suggestion of a positive association between smokingand NHL among women (OR = 1.3, CI = 0.9-1.9), although there was no clearexposure-response relationship. This large case-control analysis provides noevidence that smoking is linked to the development of NHL among men. Thepossible role of smoking in the etiology of NHL among women needs furtherevaluation.