As reported in Part 1 of this paper, the author observed a variety of electrocardiographic aberrations in 27 patients with rheumatoid arthritis. This report will compare the frequency of electrocardiographic aberrations in 45 such cases with the frequencies shown by other groups, namely : a group of 122 patients with normal blood pressure and noncardiac diseases, a group of 121 patients with hypertension, and a group of 14 patients with mitral valve diseases. The results are as follows : 1) The electrocardiographic patterns reported in Part 1 occurred more frequently in both the group of rheumatoid arthritis patients and the groups of hypertension and mitral valve disease patients than in the group with normal blood pressure and noncardiac diseases. 2) On the basis of the electrocardiographic findings, it may be assumed that many of the patients with rheumatoid arthritis suffered from pathological heart conditions, such as heart diseases or cardiac involvement, not accessible to clinical observation. 3) Patients with unequivocal cardiac involvement constituted 21 (46.6%) of the rheumatoid arthritis patients, 65 (53.7%) of the hypertension patients, 9 (64.3%) of the mitral valve didease patients, and 21 (17.2%) of the normal blood pressure and noncardiac disease patients. 4) Patients with suspected cardiac involvement, as defined in Part 1 of this paper constituted 4 (8.9%) of the rheumatoid arthritis patients, 10 (8.3%) of the hypertension patients, 1 (7.1%) of the mitral valve disease patients and 2 (1.6%) of the normal blood pressure and noncardiac disease patients.