Ornithine decarboxylase in a human parotid gland adenocarcinoma cell line was induced by both cholinergic (carbachol) and beta-adrenergic (isoproterenol) sialagogues. The enzyme protein level, measured with anti-peptide antiserum, as well as the enzyme activity, was found to be high in unstimulated cells and to increase approximately 2-fold on stimulation, while the mRNA level increased 3-4 fold, as revealed by Northern hybridization. The rise in activity was completely blocked by the simultaneous addition of antagonists or actinomycin D. These results suggest that receptor-mediated stimulation of ornithine decarboxylase activity by sialagogues involves alterations in the level of mRNA and that the proliferative responses of human parotid cells to these sialagogues resemble those of the murine parotid gland.