The present study is a revision of the patterns of the jugular and hepatic tracings, two non-invasive tracings of the venous system. The study was performed in 40 subjects; 30 of them were normal while 10 had minor conditions affecting the left heart. The time of onset and peak of the various waves was statistically evaluated in this series. In addition, 14 cases of bundle branch block and 10 cases of grade 2 or 3 atrioventricular block were studied in order to better determine the cause of certain waves. Among the findings are: 1) the presence of a double A wave in 5 normals and in over one-half of the patients with AV block; 2) the frequent occurrence of a double C wave (an occurrence that required the labeling of the two peaks as t and C both in normal subjects and in clinical cases); 3) the possibility of either a double V wave or a small V wave, followed by a large H wave, especially in hepatic tracings. The mechanism of the various waves is discussed and the possible transmission of left-sided mechanical events to the right atrium and the venous system is postulated.