An epidemiological association between periodontitis and cardiovascular disease has been reported in multiple studies. Various mechanisms have been proposed as potential explanations for this association, including a common factor that predisposes certain individuals to a hyper-responsive inflammatory response. Variations in the genes that regulate the interleukin-1 (IL-1) response have been associated with both periodontal disease and cardiovascular disease. New data indicate that one pattern of IL-1 genetic polymorphisms, characterized by the IL-1A (+4845) and IL-1B (+3954) markers, is associated with periodontitis but not certain measures of atherosclerosis. Another IL-1 genetic pattern, characterized by the IL-1B (-511) and IL-1RN (+2018) markers, is associated with atherosclerotic plaque formation, as measured by angiography and arterial wall thickness, but not periodontitis. These two patterns also have different functional implications relative to IL-1 biological activity. Studies of IL-1 gene polymorphisms, atherosclerotic plaque instability and cardiovascular clinical events are in progress. Hypothetical models are presented to explain how IL-1 genetic factors may be involved in cardiovascular disease.