In cultured human skin fibroblasts, ascorbic acid stimulates collagen production with no apparent change in the intracellular degradation of newly synthesized procollagen. To understand the basis for this effect, we measured the steady-state levels of type I and type III procollagen mRNAs in cells treated with ascorbic acid. A three- to fourfold increase in collagen synthesis was associated with a two- to threefold increase in the levels of mRNAs for both type I and type III procollagens. These effects of ascorbic acid are explained by a translational control linked either to procollagen gene transcription or mRNA degradation.