A full-length cDNA encoding rat type 2C (IA) protein phosphatase was isolated from a kidney cDNA library. The cDNA was identified by screening the library with oligonucleotides based on a partial amino acid sequence determined from purified rat liver phosphatase. This clone is 2.35 kilobase pairs long and has a single extended translation reading frame that predicts a 382-amino acid protein of 42,416 daltons. The deduced amino acid sequence contains segments corresponding to three peptides from rat liver type 2C protein phosphatase and two peptides from rabbit skeletal muscle type 2C phosphatase. Rat kidney type 2C protein phosphatase is distantly related to yeast adenylate cyclase but is not related to the catalytic subunits of two other protein phosphatases (types 1 and 2A).