mRNA coding for pre-pro-PTH, a precursor of PTH, was sought in an apparently nonfunctioning parathyroid carcinoma that had transformed from one that was previously functioning. Total poly(A+) RNA was prepared by phenol-chloroform-isoamyl alcohol extraction and oligo-dT-cellulose affinity chromatography from the tumor tissue and bovine parathyroid glands. In the rabbit reticulocyte lysate cell-free translation system, total poly(A+) RNA from the tumor as well as that from bovine parathyroid glands directed the translation of a product which was specifically precipitated by an anti-PTH serum and which migrated at the same position as pre-pro-PTH on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results indicated the presence of mRNA coding for pre-pro-PTH (PTH mRNA) in an apparently nonfunctioning parathyroid carcinoma, suggesting that PTH synthesis is not always absent in parathyroid carcinomas which are not accompanied by hyperparathyroidism.