Alterations in intracellular calcium levels activate several signal transduction pathways resulting in distinct patterns of gene expression. Here, a pathway for calcium-mediated signals is demonstrated that involves C/EBP-beta, a member of the bZip family of transcription factors. In pituitary cells C/EBP-beta was phosphorylated in response to increased intracellular calcium concentrations as a consequence of the activation of a calcium-calmodulin-dependent protein kinase. Phosphorylation of serine at position 276 within the leucine zipper of C/EBP-beta appeared to confer calcium-regulated transcriptional stimulation of a promoter that contained binding sites for C/EBP-beta.