Context: Vitamin D deficiency is associated with many adverse health outcomes, yet little is known about the genetic epidemiology of vitamin D or its metabolites. Objective: To examine the relationship between three vitamin D-related genes and levels of 25-hydroxyvitamin D (25[OH]D) and 1,25-dihydroxyvitamin D (1,25[OH]₂D) in Hispanic and African Americans. Design and Setting: Cross-sectional population-based IRAS Family Study. Participants: Subjects recruited and examined in Los Angeles, California (African Americans [AA]; 513 individuals from 42 families); San Luis Valley, Colorado (Hispanics [SLV-HA]; 513 individuals from 30 families); and San Antonio, Texas (Hispanics [SA-HA]; 504 individuals from 58 families). Main Outcome Measures: Plasma levels of 25[OH]D and 1,25[OH]₂D. Results: Levels of 25[OH]D were highest in SLV-HA (18.3±7.7 ng/mL [45.7±19.2 nmol/L]), lower in SA-HA (14.6±6.4 ng/mL [36.4±16.0 nmol/L]), and lowest in AA (11.0±5.4 ng/mL [27.5±13.5 nmol/L]). Levels of 1,25[OH]₂D were similar in AA (43.5±13.9 pg/mL [113.1±36.1 pmol/L]) and SLV-HA (43.2±13.3 pg/mL [112.3±34.6 pmol/L]), but higher in SA-HA (48.6±17.0 pg/mL [126.4±44.2 pmol/L]). After adjusting for gender and age within site, two SNPs in the vitamin D binding protein gene (DBP), rs4588 and rs7041, were associated with 25[OH]D and 1 SNP in DBP, rs4588, was associated with 1,25[OH]₂D in all three study centers. Conclusions: SNPs in DBP are associated with levels of 25[OH]D and 1,25[OH]₂D in Hispanic- and African-American participants in the IRAS Family Study.