In a multiethnic cohort of older people with diabetes (n=1178), we assessed whether ambulatory blood pressure (BP) monitoring improves prediction of all-cause mortality and cardiovascular mortality when added to baseline covariates, including office BP and heart rate (HR). Secondary analyses assessed whether albuminuria may mediate the association of pulse pressure with mortality. The ambulatory arterial stiffness index was calculated as "1-slope" from the within-person regression of diastolic-on-systolic ambulatory BP readings. Mean follow-up was 6.6+/-0.4 years. There were 287 deaths; death certificates were available for 215 deaths (75%), and 110 of them were deemed of cardiovascular cause. Cox models were built incrementally. First, models using clinical and laboratory variables selected albuminuria and office HRs as independent predictors of all-cause and cardiovascular mortality. When ambulatory monitoring data were added, sleep:wake HR ratio and ambulatory arterial stiffness index added significantly to the prediction of all-cause mortality, but only sleep:wake HR ratio added to the prediction of cardiovascular mortality. Office HR and albuminuria retained significance as predictors of both types of mortality. Secondary analyses without adjustment for albuminuria confirmed the predictive value of office HR and sleep/wake HR, whereas 24-hour pulse pressure and sleep systolic BP were also independently predictive of all-cause and cardiovascular mortality, respectively. In conclusion, office HR and albuminuria were strong predictors of mortality. Ambulatory monitoring improved the prediction of risk through its assessment of sleep HR dipping and of ambulatory arterial stiffness index, a measure of the dynamic relationship between systolic and diastolic BPs. Albuminuria may mediate the association between BP and mortality.