Pseudohypoaldosteronism type I (PHA1) is a condition associated with salt wasting leading to dehydration, hypotension, hyperkalemia, and metabolic acidosis. Sporadic cases and two familial forms, one autosomal dominant and one autosomal recessive form, have been described. The autosomal dominant or sporadic form manifests milder salt wasting that remits with age. Mutations in the gene encoding the mineralocorticoid receptor (MR) have been identified in patients with the autosomal dominant inheritance. However, recent studies suggest that the autosomal dominant and sporadic forms are genetically heterogeneous and that additional genes might be involved. We report on the study of 15 members of a Swedish five-generation family with the autosomal dominant form of PHA1. Interestingly, neuropathy was found in two of five affected individuals. A novel heterozygous nonsense mutation C436X in exon 2 was identified in the index patient by linkage analysis, PCR, and direct sequencing of the MR gene. Analysis of the family demonstrated that the mutation segregated with PHA1 in the family. It is unclear whether the neuropathy is associated with the mutation found. Our results together with previously published data suggest that loss-of-function mutations of the MR gene located at 4q31.1, commonly are associated with the autosomal dominant form of PHA1.