Monoclonal B-cell lymphocytosis (MBL) is detectable in > 3% of the general population. Recent data are compatible, at least in a proportion of cases, with MBL being a progenitor lesion for chronic lymphocytic leukemia (CLL) and a surrogate for inherited predisposition. Common single nucleotide polymorphisms (SNPs) at 2q13 (rs17483466), 2q37.1 (rs13397985), 2q37.3 (rs757978), 6p25.3 (rs872071), 8q24.21 (rs2456449), 11q24.1 (rs735665), 15q21.3 (rs7169431), 15q23 (rs7176508), 16q24.1 (rs305061), and 19q13.32 (rs11083846) have been shown to confer a modest but significant increase in CLL risk. To examine the impact of these 10 SNPs on MBL, we analyzed 3 case-control series totaling 419 cases and 1753 controls. An association between genotype and MBL risk was seen for 9 SNPs, 6 of which were statistically significant: rs17483466 (odds ratio [OR] =1.27; P = .02), rs13397985 (OR = 1.40; P = 1.72 × 10(-3)), rs757978 (OR = 1.38; P = .02), rs872071 (OR = 1.27; P = 7.75 × 10(-3)), rs2456449 (OR = 1.31; P = 3.14 × 10(-3)), and rs735665 (OR = 1.63; P = 6.86 × 10(-6)). Collectively, these data provide support for genetic variation influencing CLL risk through predisposition to MBL.