This study was performed to assess myocardial involvement in 18 children with severe hypertension (HT), using two dimensional (2D) guided M mode echocardiography, prior and during therapy. All patients but 2 had renal or renovascular disease. Septal diastolic thickness (SDT) was utilized as a serial marker. Except for one case, all patients had increased SDT initially (1.03 +/- .26 cm/m2, p less than .01 vs normal). Evolution under therapy allowed subdivision of patients: Group I: 12 patients showed left ventricular (LV) hypertrophy regression, within a follow-up period of 20 +/- 9 months (final SDT: .78 +/- .12 cm/m2 vs initial 1.09 +/- .28, p less than .01). Blood pressure (BP) was normalized in 9 patients, and borderline in 3. Therapy consisted on acebutolol (n = 10), captopril (n = 1), and renal artery surgery (n = 1). Group II: LV hypertrophy was unchanged (n = 3) or increased (n = 3), within a follow-up period of 19 +/- 8 months, with persistent severe (n = 3) or mild (n = 3) HT, under acebutolol (n = 5). Treatment was changed to captopril with subsequent normal BP and echocardiogram improvement (n = 3). In the overall population, final SDT was significantly correlated to the final BP (r = .69, p less than .01). In conclusion, echocardiographic follow-up allowed serial non invasive assessment of LV hypertrophy in our severely hypertensive pediatric population. At first echocardiogram, LV hypertrophy was present in all patients but one. Antihypertensive therapy allowed simultaneous decrease of BP and LV hypertrophy in 12 patients, 10 under acebutolol.