Little is known about the antigenic properties of human dental plaque constituents. In this work an attempt to search for the antigenic properties of dental plaque proteins was made. Rabbits and guinea pigs were immunized with solubilized samples of dental plaque, and the reactivity of obtained antisera was studied. It was found that both rabbits and guinea pigs produced specific antibodies which reacted with the plaque, serum and parotid saliva. After absorption of obtained antisera specific serum or saliva this reaction disappeared, suggesting the absence of antibodies specific for dental plaque only. It was noticed that anti-plaque antisera obtained from different species have not reacted with the same intensity. The stability of formed precipitates was also different depending on antisera. The results were discussed from the aspect of immunogenetics of protein molecules present in plaque, particularly under the conditions when their structure and conformation may be altered.