The aim of this study was to develop a planimetric, automatic method for evaluation of the extension and volume of plaque. Series of color macrophotographs of stained plaque were analyzed with a digitizer entering Cartesian coordinate data from the graphic records in a calculator. Estimations were carried out on the reproducibility, discriminatory power, and time required for the planimetric analysis. In addition, the ratios between values obtained before and after reproducible cleansing were interpreted as measurement of the adhesion of plaque in vivo.