The spatial distribution and concentration of distinct cellular elements are of interest in the evaluation of the biological reaction to implant materials, the so called biomaterials. We present a method, based on a computer assisted cell-counting program, developed to quantify the soft tissue reaction to implanted material. Five pseudomembranes formed around silicone skin expanders were studied; they were subjected to histological immunohistochemical and histomorphometrical investigation. This quantitative approach overcomes weakness due to the subjectivity of the observers and offers new possibilities when assaying the local tissue compatibility; moreover, it shows a good applicability to a wide variety of implant materials.