Pervenous endocardial pacing using a self-contained, totally implantable system was popularized in this country by Chardack in 1965 and subsequently has become the established mode of permanent pacing. Although this intervention may be lifesaving, it is not without risk. Occlusion of major vessels incited by the presence of a pacing electrode is an extremely rare occurrence. We describe four patients who had occlusion of the axillary or subclavian veins or of the superior vena cava due to pervenous pacing electrodes. We review the literature of previous observation of venous occlusion and thromboembolic complications due to pervenous pacemakers, describe the clinical features accompanying venous obstruction, and review pathophysiology and proposals for treatment. The use of noninvasive radionuclide venography serves as a useful adjunct in the diagnosis of venous obstruction from pacing catheters.