This paper deals with a simple and direct method of determining absolute values of adsorbance, i.e., mass per unit area, of polymers adsorbed from solution onto mica surfaces. The method is based on direct weighing of mica sheets using a Mettler ultramicrobalance UMT2 or UM3 (readability 1 x 10(-4) mg), which is commercially available. A set of mica sheets is weighed twice; before and after the immersion of mica sheets in polymer solution for a given period of time. The difference in weight of the mica sheets gives the mass of adsorbed polymers, which is divided by the total area of mica surface to derive the adsorbance, Measurable change in adsorbance was 0.1 mg m(-2) in consideration of the size of mica sheets (50 cm(2) in total surface area) and the scatter of readings of the ultramicrobalance. A detailed description is given on the apparatus and procedures for weighing and adsorption experiments. The present method has been applied to the experiments on the adsorption kinetics of polystyrene from cyclohexane and of bovine serum albumin from aqueous solution onto mica surfaces. Some of the experimental results are presented to show the practical examples of the application of this method. (C) Im Academic Press.