Aim of this study is to determine fibronectin concentration in the different biological materials to study its changes in the anatomic districts where the cell interactions in which FN participates do occur. The traditional immunoturbidimetric method and the nephelometric method are compared. An alternative method using a support for the collection of very small samples is proposed and the results obtained are discussed. This approach with solid phase immunonephelometry can be used both in amounts of biological fluids too small for traditional methods and in concentrations < 4.5 mg/dL. It is hoped that less complex techniques will be studied, allowing routine tests that can be performed by all laboratories. Unfortunately, at present this method is still investigated, however, it would be useful to adopt it in case of difficult sample collection.