Abstract--Antihypertensive treatment with dihydropyridines may be accompanied by sympathetic activation. Data on whether this is common to all compounds and similar in the various phases of treatment are not univocal, however. In 28 untreated essential hypertensives (age, 56.4±1.8 years; mean±SEM) finger blood pressure (BP, Finapres), heart rate (HR, ECG), plasma norepinephrine (NE, high-performance liquid chromatography), and muscle sympathetic nerve traffic (MSNA, microneurography) were measured at rest and during baroreceptor manipulation (vasoactive drugs) in the placebo run-in period and after randomization to double-blind acute and chronic (8 weeks) felodipine (10 mg/d, n=14) or lercanidipine (10 mg/d, n=14). Acute administration of both drugs induced pronounced BP reductions and marked increases in HR, NE, and MSNA. After 8 weeks of treatment, BP reductions were similar to those observed after acute administration, whereas HR, NE, and MSNA responses were markedly attenuated (-7%, -32%, and -14%, respectively; P<0.05). There was a small residual increase in sympathetic activity in the felodipine group, whereas in the lercanidipine group, all adrenergic markers returned to baseline values. Baroreflex control of HR and MSNA was markedly impaired (-42% and -48%, respectively) after acute drug administration, with a recovery and complete resetting during chronic treatment. Thus, the sympathoexcitation induced by 2 different dihydropyridines is largely limited to the acute administration. The 2 drugs have, nevertheless, a different chronic sympathetic effect, indicating that dihydropyridines do not homogeneously affect this function. The acute sympathoexcitation, but not the small between-drugs differential chronic adrenergic effect, is accounted for by baroreflex impairment.