Abstract: Method in determining hyaluronic acid by means of inhibition technique where in addition to the hyaluronic acid of the sample (analyte) a first reactant possessing hyaluronic acid structure (reactant (1), derivatized hyaluronic acid) and a second reactant possessing a hyaluronic acid binding structure (reactant (2)) are reacted with one another to form a complex in which reactants (1) and (2) are held together due to biospecific affinity. The complex is indicated by the use of a label that is attached covalently to one of the reactants or indirectly by the use of an antibody reactive with said complex. The features characteristic of the method are that (i) reactant (2) is a reactant possessing the hyaluronic acid binding structure of cartilage proteoglycan and (ii) the reaction of reactants (1) and (2) with each other is performed (a) at a pH within the range of 5.8-7.