The effect of low-yield (filter) cigarette (LYC) smoking on lung cancer risk, by two broad histologic groupings (Kreyberg I [KI] and II [KII]), was examined in a large case-control study. Among males, there were 1278 KI patients and 2408 patient controls matched on age, race, hospital, and year of interview and 807 KII patients and 1543 matched patient controls. Among females, there were 513 KI patients and 960 matched patient controls and 499 KII patients and 932 matched patient controls. For the purposes of estimating the reduction in risk due to smoking filter rather than nonfilter cigarettes, odds ratios (OR) for smokers of filter cigarettes only, short-term switchers (i.e., switchers from non-filter to filter cigarettes who had smoked the latter for 1 to 9 years), and long-term switchers (i.e., switchers to filter cigarettes who had smoked filter cigarettes for 10+ years) were calculated relative to smokers of nonfilter cigarettes only (OR = 1.00). Logistic regression was used to obtain estimates adjusted for cigarettes per day (CPD), inhalation, age, and years of schooling. Filter-only smokers of both sexes appeared to have a reduced risk of KI lung cancer (OR = 0.69, 95% confidence interval [CI], 0.37 to 1.27 in males; OR = 0.64, 0.30 to 1.35 in females). Male long-term switchers had a significantly reduced risk (OR = 0.66, 0.49 to 0.90), and female long-term switchers had a nonsignificant reduced risk of KI lung cancer (OR = 0.74, 0.40 to 1.36). The risks of short-term switchers were closer to 1.00 (OR = 0.83, 0.59 to 1.17 in males; OR = 0.99, 0.49 to 2.03 in females). Evidence of a reduction in risk of KII was weaker in males and undetectable in females.