B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) levels are increased in persons with heart failure (HF); low levels of these peptides rule out HF. We systematically reviewed the literature to assess the use of BNP and NT-proBNP in the diagnosis, prognosis, and treatment for HF. We also examined the biological variation of these peptides in persons with and without HF. We searched Medline, Embase, AMED, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and CINAHL for English-language studies published between January 1989 and June 2012. Supplemental searches involved the gray literature and the reference lists of included studies. Trained reviewers used standardized forms to screen articles for inclusion in the review and to extract data from included papers. We examined the risk of bias with QUADAS-2 for diagnosis studies, the Hayden criteria for prognosis studies, and the Jadad scale for treatment studies. We assessed the strength of evidence in four domains (risk of bias, consistency, directness, and precision) for the diagnosis and treatment studies. Results were reported as narrative syntheses. Additional meta-analyses were conducted for the diagnosis studies. Three hundred ten articles passed through screening and were included in the review. One hundred four articles applied to diagnostic accuracy, 190 papers pertained to prognosis, and nine articles addressed BNP- or NT-proBNP-guided treatment. Each individual paper in this series reports, summarizes, and discusses the evidence regarding diagnosis, prognosis, or treatment.