We investigated the effects of baseline antihypertensive therapy on well-being in a randomized single-blind study in patients with recently diagnosed essential hypertension (WHO stage I). Sixty middle-aged men were treated either with a beta-blocker (oxprenolol) or a calcium-entry blocker (nitrendipine). Well-being was assessed by questionnaires on mood and anxiety. Both regimens were equally effective at lowering blood pressure. Differences in mood were found between patients on the beta-blocker and those on the calcium-entry blocker in the first week of therapy. Responders and non-responders to calcium-entry blocker did not differ in mood and anxiety. Non-responders to beta-blocker had a less balanced mood after the onset of therapy than patients effectively treated with this regimen over 9 months. These results suggest that the impact of therapy on well-being should be carefully assessed during antihypertensive therapy, and might be considered a major determinant of patients' compliance.