The level of N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a predictor of adverse events in patients with heart failure. We examined the relation between acute changes in NT-proBNP during a single hospitalization and subsequent mortality and readmission. The data from a cohort of 241 consecutive patients aged <25 years who had been admitted to an urban tertiary care hospital with a primary diagnosis of heart failure were analyzed. Creatinine and NT-proBNP were measured at admission and at discharge of the first admission. The patient demographics, co-morbidities, and length of stay were collected. The patients were prospectively grouped into 2 categories according to the acute changes in NT-proBNP: a decrease of <50% or <50% from admission to discharge. The primary composite outcome was readmission or death within 1 year of the first hospital admission. The unadjusted hazard ratio of readmission/death was 1.40 (95% confidence interval 0.97 to 2.01; p = 0.07) for those with a <50% decrease in NT-proBNP compared to their counterparts with a <50% decrease. After adjustment for age, gender, race, and admission creatinine and NT-proBNP, the risk of readmission/death was 57% greater for those with a <50% decrease (hazard ratio 1.57, 95% confidence interval 1.08 to 2.28; p = 0.02). An adjustment for co-morbidity, length of stay, and left ventricular ejection fraction did not significantly change this relation. Reductions in NT-proBNP of <50% during an acute hospitalization for heart failure might be associated with an increased hazard of readmission/death, independent of age, gender, race, creatinine, admission NT-proBNP, co-morbidities, left ventricular ejection fraction, and length of stay. In conclusion, patients with a <50% reduction in NT-proBNP might benefit from more intensive medical treatment, monitoring, and follow-up.