The control of 18-hydroxy-11-deoxycorticosterone (18-OH-DOC) secretion is incompletely understood: ACTH seems to be the dominant regulator, the importance of angiotensin II (A-II) is uncertain, and the effect of K has not been investigated. This study evaluated the 18-OH-DOC response to these 3 stimuli in vitro. Suspensions of isolated rat adrenal glomerulosa or fasciculata cells were stimulated with either .alpha.1-24 ACTH (0.04 mU[milliunits]/ml), A-II (25 ng/ml), or K (5.9 meq/l), and 18-OH-DOC production was measured. In glomerulosa cells, ACTH produced the greatest 18-OH-DOC response but A-II and K also produced significant (P < 0.001) 18-OH-DOC increases (control, 162 .+-. 14 (SE) ng/106 cells incubated; A-II, 368 .+-. 39; K, 380 .+-. 37; ACTH, 1544 .+-. 165). In fasciculata cells, 18-OH-DOC production increased with ACTH but not with A-II or K. These results document that A-II and K, as well as ACTH, can stimulate 18-OH-DOC production by glomerulosa but not by fasciculata cells. The response to A-II may provide an explanation for the reported increase in 18-OH-DOC production after Na restriction.