Receptor- and nonreceptor-mediated stimuli produce increases in both PKCdelta tyrosine phosphorylation and activity in rat parotid acinar cells and other cells. In vivo and in vitro increases and decreases in tyrosine phosphorylation resulted in increases and decreases, respectively, of PKCdelta activity. These studies demonstrated that increases in PKCdelta activity by G protein-coupled receptors and other stimuli were controlled by alterations in tyrosine phosphorylation.