Eighteen acromegalic patients (A) and 18 controls without clinical evidence of cardiac involvement and/or endocrine disease (C), matched for sex, age, body surface area, and blood pressure (BP), were investigated by M-mode (2-D derived) echocardiography, to clarify the prevalence and the possible determinants of left ventricular hypertrophy (LVH). Seven patients in each group were hypertensive (BP greater than 160/95 mmHg). Left ventricular mass (LVM) was 183.1 +/- 60.0 g/m2 in A and 130 +/- 25.9 g/m2 in C. A LVM above 140 g/m2 (that is the upper normal range in our laboratory) was found in 15/18 A and 2/18 C. The LVH was concentric (h/r greater than 0.45) in 12/15 A and 1/2 C. Systolic function indexes (% FS, end-systolic stress/end-systolic volume), cardiac index and total peripheral resistance index (as determined by echo) were within the normal range and similar in both groups. No correlation was found between LVM and BP, LVM and GH plasma levels, LVM and Sm-C levels. A significant correlation was found between LVM and duration of the disease (r 0.44; p less than 0.05). Our data confirm that LVH is an early and frequent finding in acromegaly. Its prevalence is not entirely accounted for by such factors as body size, BP or increased cardiac output. Metabolic factors may play a major role, and a long lasting exposition to increased GH levels seems the most relevant determinant of LVH.