Analytical gel filtration was used for the study of molecular size dis
tribution of clinical dextran in serum and urine for the purpose of ev
aluations of changes in the human glomerular barrier function. The col
umn was calibrated in terms of solute size using a simple and accurate
technique recently described. Only one sample of a dextran possessing
a broad molecular mass distribution was necessary for the calibration
procedure and the calculations were performed using an ordinary sprea
dsheet. The accuracy of the calibration, as evaluated by protein sampl
es, is better than 95%. The simplicity makes the method suitable for u
se in laboratories not normally specializing in analytical gel filtrat
ion. Calibration in terms of size is preferably done with respect to v
iscosity radius to obtain relevant information about the permeability
of dextran into porous membranes.