While sequence information is available for a number of eukaryotic protein phosphatase 1 (PP1)-encoding genes, the cloning and characterization of a complete human pp1 gene has not been reported. We have used two conserved regions within the pp1 family of genes to synthesize oligodeoxyribonucleotide primers for the amplification of a 438-bp sequence from human mRNA. This DNA fragment was sequenced to verify that it corresponded to a pp1 cDNA and it was used to screen a human cDNA library to isolate a full-length clone. The deduced amino acid (aa) sequence identified a protein of 330 aa in length. Comparison with the rabbit pp1 cDNA sequence showed some nucleotide differences, largely at the third position of the codon, with complete concordance at the aa level. Northern blot analysis revealed an mRNA of approximately 1.6 kb.