Objective To investigate the effects of dialysis procedures on cardiac diastolic function. Design Comparative, nonrandomized matched pair study. Setting Nephrology and cardiology departments at a university hospital. Patients Thirty-four patients on hemodialysis (HD) (n = 17) and continuous ambulatory peritoneal dialysis (CAPD) (n = 17), matched by sex, age, duration of dialysis treatment, and presence/absence of diabetes. Measurements Cardiac function was estimated by means of M-mode, two-dimensional, and spectral Dopplerechocardiography, and results were statisticallyevalu-ated by means of univariate and multivariate analytical procedures. Results Although not statistically significant, trends towards differences between the two patient groups were detected for left ventricular mass (p = 0.083) and parameters of diastolic function (p = 0.079). These differences in left ventricular performance and diastolic function between HD and CAPD patients were also evident when calculating Spearman rank correlation coefficients. Left ventricular mass and diastolic function were closely correlated to each other in all dialysis patients. Moreover, by means of a multivariate analytical procedure (Hotelling T square test), diversities in diastolic function between the two patient groups could be clearly established (p = 0.037), with more impaired diastolic function in HD patients. In addition, cardiac performance was shown to depend to a certain extent on hemoglobin concentration. Conclusion Clear differences in diastolic function and cardiac performance were evident between CAPD and HD patients. From the data of our pilot study, it may be speculated whether decrease of left ventricular mass could be beneficial for the improvement of diastolic function and cardiac hemodynamics in dialysis patients.