Novel single nucleotide polymorphisms in the human natriuretic peptide receptor A/guanylate cyclase A (atrionatriuretic peptide receptor A) (NPR1) gene are described. In addition, various genotypes, haplotypes and haplotype pairs for the NPR1 gene that exist in the population are described. Compositions and methods for haplotyping and/or genotyping the NPR1 gene in an individual are also disclosed. Polynucleotides containing one or more of the NPR1 polymorphisms disclosed herein are also described.