To assess the frequency and degree of valvular regurgitation in combined heart and lung transplant recipients, 50 patients were investigated using Doppler color flow echocardiography 20 to 909 days (mean 369) after heart-lung transplantation. The mean age (+/- SD) of the patients was 25 +/- 9 years. No patient had evidence of rejection at the time of the study. Fifty normal volunteers acted as control subjects. Tricuspid, mitral and pulmonary regurgitation were commonly observed in the patients undergoing heart-lung transplantation (78%, 52% and 68%, respectively), but were not significantly more frequent than in the normal subjects (68%, 42% and 70%, respectively). Aortic regurgitation was uncommon in both groups (4% and 2%, respectively). However, tricuspid and mitral regurgitant jet areas were significantly greater (p less than 0.01) in heart-lung transplant recipients than in normal subjects (156 +/- 120 and 84 +/- 52 mm2 compared with 40 +/- 38 and 28 +/- 26 mm2, respectively); pulmonary regurgitant jet area was not significantly different in the two groups (32 +/- 26 and 28 +/- 26 mm2, respectively). Regurgitant jet area was not significantly correlated with patient or donor age, donor organ total ischemic time, time after operation, use of steroids for immunosuppression or total number of rejection episodes. These results show that valvular regurgitation is not significantly more frequent after heart-lung transplantation than in normal subjects, but atrioventricular (AV) valve regurgitation, when present, is significantly greater in degree. This suggests that the degree but not the frequency of AV valve regurgitation is related to transplantation.