The release of growth hormone, prolactin and cortisol following oral imipramine was studied in nine fit young men. Imipramine 100 mg, but not 40 mg, led to reliable rises in the circulating levels of all three hormones in the majority of subjects. These responses are likely due to the enhancement of central noradrenergic and serotonergic function as a result of reuptake inhibition. The safety, sensitivity and reliability of these responses make imipramine 100 mg orally a potentially valuable neuroendocrine challenge test.