Dexamethasone pharmacokinetics were measured in 19 depressed patients, 10 dexamethasone suppression test (DST) nonsuppressors and nine suppressors, following a 1 mg oral dose in tablet form at 2300 h. Median dexamethasone concentrations were significantly lower in the nonsuppressors from 3-16 hr post-administration. Nonsuppressors had a significantly lower area under the curve than suppressors, and plasma clearance was significantly faster in the nonsuppressors than in the suppressors. Eleven patients, six nonsuppressors and five suppressors, agreed to a repeat DST after clinical improvement when all six nonsuppressors had normal DST responses. There were no significant differences between the median dexamethasone concentrations, or any of the pharmacokinetic parameters measured, of the "normalising" nonsuppressors and the suppressors. Dexamethasone kinetics were altered in depressed nonsuppressors but became normal with remission of depressive symptoms and normalisation of the DST response.