BACKGROUND: Measurement of B-type natriuretic peptide (BNP) in plasma may have its greatest potential in primary care, as general practitioners need to rapidly identify patients who warrant further medical review. The aim of the present study was to examine the prognostic information of BNP measurement on all-cause mortality in a large Danish primary care cohort. METHODS: This study covered a cohort of Danish primary care patients (n = 61665) with a median follow-up period of 4.36 years (interquartile range, 2.29-6.62 years). BNP was measured in plasma using the ADVIA Centaur/ CentaurXP platform. The association of BNP with mortality was assessed with a hazard ratio for all-cause mortality from a multivariable Cox proportional hazards model. RESULTS: Kaplan-Meier curves showed decreasing survival probability with increasing BNP (P < 0.001). Each doubling of BNP increased mortality by 32.3% (95% CI, 30.8-33.8) when adjusted for sex and age, and by 25.3% (95% CI, 23.8-26.8) when further adjusted for Charlson comorbidity index, hemoglobin, estimated glomerular filtration rate, glycohemoglobin, and thyroid-stimulating hormone. Also, in a subcohort (n=10824) without biochemical signs of severe kidney failure, anemia, polycythemia, hypothyroidism or hyperthyroidism, or dysregulated diabetes, each doubling of BNP increased mortality by 28.6% (95% CI, 22.8-34.7). CONCLUSIONS: Our results show that even in a primary care population, BNP measurements contain prognostic information regarding all-cause mortality.