We cloned a cDNA coding for rat protein C, which provides hybridization probes for the detection of protein C mRNA in several tissues. The cloned cDNA was 1543 bp long and contained a single open reading frame of 1383 nucleotides. The proposed rat protein C precursor contained 461 amino acid residues: a 41 amino acid preproleader sequence, and light (155 amino acids) and heavy (263 amino acids) chains joined by a Lys-Arg dipeptide. Northern blot analysis showed that the rat protein C mRNA was expressed not only in the liver, but also in the kidney.