Background Altered levels of von Willebrand factor (vWF) and ADAMTS13 can promote thrombosis and disturb blood flow in kidney microcirculations. We investigated the association of serum vWF:ADAMTS13 ratio in relation to decline in kidney function. Study Design Prospective cohort study. Setting & Participants 2,479 individuals (mean age, 65.1 ± 5.9 [SD] years; 43% men) from the population-based Rotterdam Study. Predictors vWF, ADAMTS13, and vWF:ADAMTS13 ratio. Outcomes & Measurements Annual decline in estimated glomerular filtration rate (eGFR), halving of eGFR, and new-onset eGFR