In this work electrophoretic mobility as well as molecular weight of dental plaque proteins were examined. Three types of electrophoresis and three procedures for molecular weight estimation were applied. The results showed that the electrophoretic mobility of some protein fractions present in plaque corresponded to the mobility of human serum albumin, albumin, alpha 1, alpha 2, beta and gamma globulins. The molecular weight of these proteins was estimated as to be 65,000 to 900,000 daltons approximatively. Electrophoretic mobility and molecular weight of dental plaque proteins were similar to the physicochemical properties of human serum albumins, alpha 1 anti-tripsin, transferin, some of the components of complement system, to secretory IgG and to some categories of lipoproteins, all of which we have identified immunochemically in human dental plaque samples.