Limited information is available comparing the relative longitudinal effectiveness with respect to tooth type of scaling and root planing alone and scaling and root planing followed by flap procedures. The purpose of this study was to investigate these treatment methods as applied to molar and nonmolar teeth on a longitudinal basis in humans. Seventeen subjects with chronic periodontitis received thorough scaling and root planning as well as oral hygiene instruction. A modified Widman flap was then randomly performed for one-half of each subject's dentition. Routine recall prophylaxis and oral hygiene reinforcement were administered postsurgically every 3 to 4 months. Pocket depth and clinical attachment levels were recorded by a single calibrated examiner before therapy and at intervals up to 61/2 years following active treatment. Ten subjects remained as participants after 61/2 years. A paired t test was used to test for the mean difference in pocket depth and clinical attachment level between molar and nonmolar teeth for each treatment method. For pockets initially 4 to 6 mm, the results indicated greater pocket depth and more apical clinical attachment level on molars than nonmolars treated by either method of therapy. For pockets initially greater than or equal to 7 mm there was no difference between pocket depth on molar and nonmolar teeth following scaling and root planing alone. However, there was less overall pocket depth on nonmolars than molars following the flap procedure, indicating a greater effect of pocket reduction on nonmolar than molar teeth with the flap procedure. No difference between tooth types was found for clinical attachment level in pockets initially greater than or equal to 7 mm with either treatment method. Both treatment methods resulted in at least maintenance of pretreatment attachment levels adjacent to molar and nonmolar teeth.