The destructive action of chronic periodontitis on the periodontal tissues has provided a continuing challenge to the dental profession to develop better methods to achieve repair of the resulting lesion and even regeneration of lost tissues. A current account of some of the methods used and their relative efficacy can be obtained from recent reviews. A number of reports exist on the clinical results obtained after various new attachment procedures. Some reports are based on a relatively large number of treated lesions, a varying proportion of which have been reentered surgically to check on the type of healing which had taken place. The overall impression is that 3-wall intrabony defects heal more completely than 2-wall defects, and these in turn heal better than 1-wall defects. However, considerable variation exists in the amount of new attachment reported by various investigators for different treatment procedures. A number of studies have been carried out in various animal models where defect standardization and histological studies are more easily performed. Such studies may provide useful information about certain principles of wound healing, but cannot be directly extrapolated to the therapy of human lesions. Relatively few histological studies exist on the effect of various therapeutic procedures in human lesions. This investigation was carried out to document clinically and histologically the response of human chronic periodontitis lesions treated with curettage and root planing only, or with the use of osseous autografts or allografts, with and without root planing.