We investigated the effects of various Ca channel agonists (Ca agonist) derived from 1,4-dihydropyridine on KCl-stimulated 45Ca uptake by differentiated and undifferentiated neuroblastoma x glioma hybrid NG108-15 cells with and without dibutyryl cAMP. Ca agonists Bay K 8644, YC-170 and CGP 28392 enhanced KCl-stimulated 45Ca uptake in differentiated NG108-15 cells, but only slightly in undifferentiated NG108-15 cells. The rank order of the enhancing effects was roughly Bay K 8644 > YC-170 > > CGP 28392. These results suggest that there is some difference between the mechanism by which these Ca agonists affect KCl-stimulated 45Ca uptake in differentiated and undifferentiated NG108-15 cells, although the nature of that difference is not clear.