The study presents an evaluation of the effectiveness of subgingival scaling and root planing related to depth of pocket and type of teeth. A total of 199 teeth in 25 patients were selected; 62 were scaled and 57 were used as controls. All teeth were initially scored using the calculus index of the P.D.I. (Ramfjord). Six surface locations were probed to determine pocket depth. The levels of the gingival margin were marked on the teeth to locate supra and subgingival calculus after extraction. The experimental teeth then were scaled. Both scaled and unscaled teeth were extracted immediately after the experimental procedures. The teeth were washed with water and stained with methylene blue. They were viewed under a stereomicroscope which had a tenth grid on its eyepiece. Percent of surface covered by calculus was assessed on both scaled and unscaled teeth. The results demonstrated a high correlation between percent of residual calculus and pocket depth. It was shown that pockets less than 3 mm were the easiest sites for scaling and root planing. Pocket depths between 3 to 5 mm were more difficult to scale and pockets deeper than 5 mm were the most difficult. Tooth type did not influence the results.