Introduction The aim of this investigation was to evaluate and compare the pulp stump wounds created by the following root canal instruments: ProFile rotary files and small-diameter fine diamond burs. Methods Extracted mandibular premolars from adult patients with vital pulps and fully formed root canals were collected and stored in formalin. Within 48 hours of extraction, the periapical tissue was fixated to the root with a double coating of ethyl cyanoacrylate, and the pulp chambers were accessed with a #4 round carbide bur and high-speed handpiece in a traditional fashion. The pulp tissue of 10 specimens per group was extirpated at a level approximately 5 mm from the apex by using standard endodontic techniques. The specimens were then examined at ×100 magnification under a digital microscope. Grading criteria were developed, and the wounds were scored. Results Wounds created by diamond burs were significantly smoother that those created by ProFile rotary files; the mean wound score for diamond burs was 1.4 versus a mean wound score of 3 for ProFiles. After the author's scoring of the wounds, 2 endodontist graders were shown photos of each specimen in a double-blind fashion and instructed to score each specimen as being smooth or rough. To validate the developed scoring system and remove potential observer bias of the author, the data from the double-blind observations were used to complete a cross-tabulation for a Cohen kappa test. Conclusions Kappa values demonstrated substantial inter-rater agreement for both groups. © 2014 American Association of Endodontists.