Variants in the APOL1 gene are associated with kidney disease in blacks. We examined associations of APOL1 with incident albuminuria and kidney function decline among 3030 young adults with preserved GFR in the Coronary Artery Risk Development in Young Adults (CARDIA) study. eGFR by cystatin C (eGFRcys) and albumin-to-creatinine ratio were measured at scheduled examinations. Participants were white (n=1700), high-risk black (two APOL1 risk alleles, n=176), and low-risk black (zero/one risk allele, n=1154). Mean age was 35 years, mean eGFRcys was 107 ml/min per 1.73 m(2), and 13.2% of blacks had two APOL1 alleles. The incidence rate per 1000 person-years (95% confidence interval) for albuminuria over 15 years was 15.6 (10.6-22.1) for high-risk blacks, 7.8 (6.4-9.4) for low-risk blacks, and 3.9 (3.1-4.8) for whites. Compared with whites, the odds ratio (95% confidence interval) for incident albuminuria was 5.71 (3.64-8.94) for high-risk blacks and 2.32 (1.73-3.13) for low-risk blacks. Adjustment for risk factors attenuated the difference between low-risk blacks and whites (odds ratio 1.21, 95% confidence interval 0.86-1.71). After adjustment, high-risk blacks had a 0.45% faster yearly eGFRcys decline over 9.3 years compared with whites. Low-risk blacks also had a faster yearly eGFRcys decline compared with whites, but this difference was attenuated after adjustment for risk factors and socioeconomic position. In conclusion, blacks with two APOL1 risk alleles had the highest risk for albuminuria and eGFRcys decline in young adulthood, whereas disparities between low-risk blacks and whites were related to differences in traditional risk factors.