The relationships between periodontitis and systemic disease and conditions, environmental factors, and behavioral influences are evolving rapidly. Success in preventing and treating periodontal diseases may well rest to a large extent on our understanding of the relevant influences which may exacerbate and perpetuate the disease process. As researchers work to clarify these relationships, we as practitioners must continue to alter our treatment in the best interests of the patient's overall health. The impact of recent findings on the development and progression of periodontitis relevant to diabetes mellitus, HIV, genetic susceptibility, smoking, stress, and osteoporosis is reviewed.