Left ventricular systolic and diastolic function was studied using systolic time intervals and echocardiography in 19 male and 17 female patients with Type 1 (insulin-dependent) diabetes, 24 male and 15 female patients with Type 2 (non-insulin-dependent) diabetes and 24 male and 24 female control subjects. The subjects for the present study were selected from a population based study in which 117 Type 1 and 510 Type 2 diabetic patients and 649 non-diabetic subjects were originally examined. After exclusions, none of the subjects had any evidence of coronary heart disease, hypertension or other diseases known to affect left ventricular function. There were no consistent differences in systolic time intervals or echocardiographic variables of systolic function between patients with Type 1 diabetes and non-diabetic control subjects; but patients with Type 2 diabetes showed an increased fractional shortening. Female patients with Type 2 diabetes showed an increased left ventricular mass not explicable by hypertension. Isovolumic relaxation period was longer in male (86 +/- 3 ms; mean +/- SEM) and female patients (84 +/- 6 ms) with Type 2 diabetes than in male (76 +/- 3 ms; p less than 0.05) and female (71 +/- 3 ms; p less than 0.05) control subjects. Peak diastolic filling rate was lower in female patients with Type 1 diabetes (12.8 +/- 0.8 cm/s, p less than 0.05) and in male (11.5 +/- 0.8 cm/s; p less than 0.01) and female patients (11.5 +/- 0.6 cm/s; p less than 0.001) with Type 2 diabetes as compared to male (14.4 +/- 0.7 cm/s) and female (14.9 +/- 0.5 cm/s) control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)