The factors controlling levels of peptidyl glycine alpha-amidating monooxygenase (PAM) activity in its major tissue sources in the adult male rat were investigated by carrying out a variety of endocrine, pharmacological, and dietary manipulations. Levels of PAM activity and alpha MSH immunoactivity in the neurointermediate lobe of the pituitary gland rose and fell in parallel in rats treated with the dopamine antagonist haloperidol or the dopamine agonist bromocriptine, respectively. PAM activity in the anterior pituitary lobe was increased after adrenalectomy or castration and decreased after thyroidectomy or treatment with haloperidol. PAM activity in the submandibular gland was increased after treatment with the alpha-adrenergic antagonist phenoxybenzamine and decreased after treatment with the alpha-adrenergic agonist phenylephrine. Serum levels of PAM activity were unaltered after hypophysectomy, adrenalectomy, sialectomy, or castration, but rose after thyroidectomy and declined after treatment with the ganglionic blocker chlorisondamine or phenoxybenzamine. Chronic dietary copper deficiency in rats resulted in increased PAM activity in homogenates of anterior pituitary lobe and submandibular gland assayed under optimized conditions; chronic dietary ascorbate deficiency in guinea pigs did not produce consistent changes in PAM activity in the tissues examined.