The effect of yohimbine treatment (4 mg three times daily) for 3 weeks on salivary secretion was investigated. In healthy volunteers, acute administration of yohimbine increased salivary volume within 1 h to a similar extent before and at the end of the treatment period. In depressed patients treated with tricyclic antidepressants (and exhibiting a reduced salivary flow), yohimbine also acutely increased salivary volume. In contrast, the alpha 2-adrenoceptor antagonist failed to modify resting values measured in the morning (i.e. 10 and 14 h after the last administration in healthy volunteers and depressed patients respectively). This result indicates that alpha 2-adrenoceptor antagonists may have a potential therapeutic use in the treatment of dry mouth caused by tricyclic antidepressant drugs.