This paper evaluates the hypothesis that Black smokers will respond differently than Whites to a smoking cessation intervention program where no adjustments are made in recognition of cultural differences. The responses of Black smokers who were recruited into the Lung Health Study (LHS) to the smoking cessation intervention are described. Black quit rates are compared with those of Whites. The LHS enrolled 5887 men and women smokers, aged 35-60 years, of whom 3923 were randomized to a group cessation intervention and 1964 to usual care. Blacks and Whites from six clinics who had complete covariate data (200 Blacks and 2868 Whites) were compared on baseline smoking characteristics and subsequent smoking cessation outcomes. Logistic models were constructed to adjust for baseline smoking variables and demographic characteristics to evaluate the effect of treatment group on smoking cessation among Blacks and Whites. At baseline, Blacks reported smoking fewer cigarettes than Whites, but had higher mean levels of salivary cotinine. The adjusted odds ratio of quitting at 1 year for the smoking intervention group vs. the usual care group was 1.48 for Blacks and 5.99 for Whites. This difference between Blacks and Whites was highly significant (p = 0.002). Across 5 years, the adjusted odds ratios of quitting were 1.87 for Blacks and 3.34 for Whites (p = 0.06). Although the treatment effect was stronger for Whites than for Blacks, over the 5 years of the study there was a significant treatment effect for Blacks. Indicators of physical dependence on nicotine at baseline were inconsistent in indicating whether Blacks were more dependent. We conclude that Blacks and Whites differed significantly in their response to the LHS group smoking intervention program.