A new system for lectin-glycoprotein complexes dissociation constants (K) determination is presented. The system is based on agarose affinity electrophoresis where equal lectin (Con A) concentrations are inhibited by variable specific sugar (.alpha.-methyl-mannoside [.alpha.-MM]) amounts. Moreover, the system allows lectin-sugar inhibition constants (Ki) studies. For determination of mechanisms as well as K and Ki values calculations mathematical equations are developed. Values of K for two variants of .alpha.1 acid-glycoprotein, two variants of .alpha.1-antitrypsin, one variant of alphafetoprotein and Ki for Con A-.alpha.-MM are calculated according to the introduced equations and compared in a computed system. Moreover, the influence of sugar on lectin-glycoproteins interaction is demonstrated and discussed.