Glomerular ultrafiltration of macromolecules is a biophysical process sharing both a diffusive and a convective component, governed by glomerular hemodynamics, through a composite structure, the glomerular filtration barrier. Studies of the fractional clearance of macromolecules have showed that transcapillary filtration of macromolecules is hindered by size, electrostatic charge and to a lesser degree by spatial conformation. Several modelizations of ultrafiltration have been developped to quantify the respective role of glomerular hemodynamic and/or membrane structural alternations as found in glomerular diseases.