Twenty-four-hour blood pressure (BP) and heart rate profiles were recorded in 19 patients 1 and 7 months after cardiac transplantation using noninvasive ambulatory monitors and were analyzed using the periodogram method. These recordings were compared with those of control subjects matched for age, sex and daytime ambulatory BP. One month after transplantation, the nighttime decrease in systolic and diastolic BPs were attenuated in the patients as compared to the control subjects (p less than 0.001). The daily oral dose of prednisolone was inversely correlated with the magnitude of the nighttime decreases in systolic and diastolic BPs (r = -0.47 and -0.53, p less than 0.05). In contrast, 7 months after transplantation, the nighttime decrease in systolic and diastolic BPs reappeared in the patients and was of similar magnitude as that in the control subjects. When the immunosuppressive regimens during the 2 periods of recordings were compared, the reduction in the daily oral dose of prednisolone administered to the patients 7 months after transplantation was correlated with the observed increase in the day-night systolic and diastolic BP difference (r = 0.61, p less than 0.01 and r = 0.51, p less than 0.05). Thus, data show the reappearance of normal circadian BP profiles in patients with long-term heart transplants, and suggest that glucocorticoid administration may contribute to the abnormal nocturnal BP profiles observed 1 month after transplantation.