The left ventricular diastolic and systolic functions were assessed in 27 strictly selected type 1 diabetic patients without overt heart disease and 50 age- and sex-matched control subjects. For evaluating left ventricular performance, complex mechanocardiography including digitized apexcardiography was used at rest and after symptom-limited, graded dynamic exercise. The values of diastolic/systolic time intervals and amplitude parameters did not differ significantly between the diabetic and control groups at rest. A longer value of corrected early apexcardiographic relaxation time (diabetics: 38.7 ± 2.6 ms, controls: 17.3 ± 2.1 ms, p < 0.001) and a smaller normalized amplitude of relaxation (diabetics: 0.014 ± 0.004 ms<sup>-1</sup>, controls: 0.056 ± 0.006 ms<sup>-1</sup>, p < 0.001) were observed after dynamic exercise suggesting disturbances of the early diastole in diabetic patients. No correlations could be found between the diastolic abnormalities and the diabetic control. Significant correlation was observed between the diastolic disorders and the duration of diabetes mellitus. Testing left ventricular performance by complex mechanocardiography including digitized apexcardiography after dynamic exercise in patients with type 1 diabetes might be useful for recognizing diastolic abnormalities even when no alterations could be identified at rest. Diastolic disorders could appear in diabetic patients without overt heart disease and clinical symptoms. Left ventricular systolic function might be normal, although exercise-induced alterations of diastolic function might already be present in type 1 diabetic patients.