Effects of dietary chloride ions on the levels of both cytochrome P-450aldo (CYP11B2) and angiotensin II receptors were examined in rat adrenals. Capsular adrenal CYP11B2 protein levels significantly increased in previously chloride-depleted animals treated with either ammonium- or choline chloride. No changes in CYP11B2 protein levels were detected in previously chloride-depleted rats replenished with either ammonium acetate or choline bromide. The induction of CYP11B2 by chloride-repletion was not concurrent with either increased plasma renin activity or elevated serum potassium levels. None of the above dietary manipulations affected angiotensin II receptor number and affinity, respectively. Treatment of chloride-repleted animals with an angiotensin II receptor antagonist (TCV116) significantly attenuated the increase of CYP11B2 protein levels. In addition, chloride-repletion of previously chloride-depleted animals increased mRNA levels encoding angiotensin II type 1B receptor, but decreased mRNA levels encoding the type 1A form of the receptor. Thus, the presented data are supportive of the notion that the regulation of CYP11B2 expression in the capsular portion of the rat adrenal is, in part, mediated via induction of the angiotensin II type 1B receptor.