For careful analysis of His bundle electrograms in the dog it is useful to have a stable rather than moving recording site. In this study we have compared the characteristics of His bundle electrograms recorded by two methods in each of ten anesthetized dogs. Records obtained with a Hoffman-type plaque electrode sutured in the vicinity of the His bundle were not significantly different from ones obtained with a recording catheter wedged in the aortic root. In addition to measurements made during the resting state, comparisons also included those during selectively produced acute but transient complete A-V block, sinus bradycardia, A-V junctional tachycardia, A-V junctional bradycardia, and various degrees of incomplete A-V block. A stable and accurate His bundle electrogram can be obtained from the aortic root and has the experimental advantage of not having to open the right atrium or place sutures near the A-V node or His bundle. © 1975.