A retrospective analysis was carried out to determine the frequency and onset of endodontic complications occurring in 52 patients treated for advanced periodontal disease. Comparisons were made between teeth which, following periodontal treatment, were used as abutments in fixed prosthetic reconstructions and nonabutment teeth. The study included 672 teeth with initially vital pulps (255 abutment teeth and 417 nonabutment teeth). The observation period varied from 4 to 13 years with a mean of 8.7 years. Pulpal necrosis including periapical lesions developed with a significantly higher frequency in abutment teeth than in nonabutment teeth (15% vs. 3%). The majority of these lesions did not appear until several years following the completion of active treatment. Conceivable reasons for the development of pulpal necrosis in teeth subjected to combined periodontal and prosthetic treatment are discussed.