Effector-target conjugation is described quantitatively by binding isotherms which are characterized by three parameters, the maximum effector and target conjugate frequencies, α m a x and β m a x , and the dissociation constant of the conjugates formed, K D . In this paper the application of non-linear data-fitting techniques, as well as linear transformations of the binding isotherms that permit us to use standard regression analysis, has been tested to calculate estimates of these parameters in the NK-MOLT4 and NK-K562 effector-target systems. Both unweighted and weighted data were used to calculate α m a x , β m a x and K D for six different donors which were used as a source of NK cells. The results obtained have shown that these regression methods are useful for revealing potential disparities between binding efficiencies in effector-target systems.