This study evaluated the effects of chemical and biologic agents on periodontally diseased root surfaces which had been scaled or root planed. The proximal surfaces of 25 teeth were scaled to remove all visible calculus, and the proximal surfaces of another 25 teeth were vigorously root planed to remove all cementum and to achieve a hard, smooth, glass-like surface. Five scaled and five root planed specimens were randomly selected for light microscopic examination to determine the amount of cementum removed. Cementum remained on all scaled surfaces but root planing had removed most of the more coronal cementum. Each of the 40 remaining teeth (20 scaled and 20 root planed) was longitudinally sectioned to obtain an experimental and control specimen. Four scaled and four root planed sections were randomly selected as experimental specimens for a test of each of the following five agents: (1) saturated citric acid for three minutes; (2) 15% EDTA for 5 minutes; (3) sodium hypochlorite for 5 minutes, followed by a 30-second application of 5% citric acid; (4) sodium hypochlorite alone for 5 minutes; and (5) 2% sodium deoxycholate (NAD) for 1 minute, followed by a 1-minute rinse in distilled water, and then a 1-minute application of 5% Cohn's fraction IV1. The control for each experimental specimen was treated with saline. All samples were prepared for SEM and examined at 3,000 X. Areas of particular interest were also examined at 12,000 X. The chemical treatments exposed only individual collagen fibers or irregular fiber bundles on the scaled surfaces. Saturated citric acid, EDTA, and sodium hypochlorite with citric acid neutralization removed debris and exposed openings in the root surfaces. Sodium hypochlorite alone and NaD/Cohn's fraction IV1 were less effective in removing surface debris and had an effect similar to that seen in the saline controls. Application to root planed specimens of saturated citric acid, EDTA, and sodium hypochlorite followed by 30 seconds of citric acid neutralization resulted in surfaces virtually free of debris and with numerous collagen fibers exposed on the surface. EDTA appeared to cause a morphologic change in the collagen fibers. Sodium hypochlorite alone, sodium deoxycholate followed by Cohn's fraction IV1, and physiologic saline were relatively ineffective in surface debridement.