OBJECTIVE--To study regional wall motion of the systemic ventricle in patients after the Fontan operation. DESIGN AND PATIENTS--Systemic ventricular angiograms of 15 patients after the Fontan operation and of 11 unoperated patients with a univentricular atrioventricular connection were digitised frame by frame. Strict criteria for abnormal wall motion were used so that minor abnormalities were not considered. RESULTS--Incoordinate contraction of the ventricular wall was found in five of the 11 patients before and in four of the 15 patients after the Fontan operation (NS). Only three of the 11 patients before the Fontan operation, showed incoordination of ventricular relaxation, but incoordinate relaxation was seen in 12 of the 15 patients after operation (p less than 0.01). CONCLUSIONS--Whereas incoordination of ventricular contraction was common in patients with a univentricular atrioventricular connection, before or after the Fontan operation, incoordinate relaxation of the ventricular wall was a common consequence of the Fontan operation and was rare in patients before operation.