The effect of oral administration of carbamazepine for a period of three weeks on serum growth hormone, serum immunoreactive insulin, and blood glucose was studied in healthy volunteers using a levodopa stimulation test. Serum growth hormone rose significantly from 1.3 +/- 0.3 ng/ml to 16.3 +/- 3.4 ng/ml in 60 minutes after levodopa administration (1000 mg orally) before carbamazepine, and almost similarly from 2.3 +/- 0.5 ng/ml to 15.1 +/- 4.0 ng/ml after carbamazepine during the test. No consistent changes were found in blood glucose concentrations in the levodopa test before or after carbamazepine. Levels of serum IRI were also normal throughout the test and no impairment in insulin secretion was seen during carbamazepine treatment. It is suggested that carbamazepine does not lead to an altered anterior pituitary function or to an impairment in insulin secretion. This is of advantage when growing children or subjects with a risk factor for diabetes are treated.