This study has several strengths. We performed a GWAS and candidate gene study investigating a variety of smoking behaviors with public health importance for the first time in a sample unselected for smoking behaviors and/or smoking attributable disease. We confirm important findings from recent GWAS and candidate gene studies of nicotine dependence and CPD. Our sample size is relatively large, yet still not large enough to reliably detect variants with modest effects on smoking behaviors. The absence of selection bias in the cohort bases for the samples enhances generalizability to U.S. non-Hispanic whites although a modest limitation is that the education level in both cohorts is above average. By limiting analyses to subjects of European ancestry and adjusting for principal components of population structure, we minimized risk of false positives due to population stratification, but are not be able to detect SNP alleles associated with smoking behavior that are common in non-Europeans but rare among European-Americans. The smoking behavior characteristics for the two studies are quite similar after taking into account expected differences by gender (Table 1), and the correlation
