The early recognition of acute rejection after heart transplantation remains an important clinical problem. In this study we explored the value of echo-Doppler techniques to identify the rejection during the first week after cardiac transplantation. The study included 22 patients with an average age of 48 +/- 9 years. Ultrasonic measurements were obtained by 2-dimensional 84 degrees phased array sector scanner with pulsed Doppler incorporated. The stroke index (SI), the peak outflow blood velocity pulsed (POBVP), the peak outflow blood acceleration pulsed (POBAP), the peak flow velocity in early diastole (PFVE), the peak flow velocity during atrial systole (PFVA), the PFVA/PFVE ratio, the mitral valve pressure half-time (PHT) and the fractional shortening (FS) were calculated. On the seventh day after transplantation, a percutaneous right ventricular endomyocardial biopsy was systematically performed. For the entire group, the SI, PHT and the FS relation were not significantly influenced during the week of evaluation. The POBVP and the POBAP transiently decreased but returned to baseline on the seventh day. An increment in the PFVA/PFVE ratio was observed in 4 patients, and acute allograft rejection was documented in 3 of them. On day 7 after transplantation, PFVA and PFVA/PFVE were significantly higher in patients with rejection. No patient with normal PFVA/PFVE ratio had allograft rejection. No patient with rejection showed signs of altered systolic function as measured by SI, POBVP, POBAP and FS. These data therefore indicate that the assessment of the diastolic function using Doppler techniques (PFVA/PFVE) can be helpful to detect signs of acute allograft rejection occurring early after heart transplant.