The activation of the complement system by polymer materials and their blood compatibility. One of the negative effects of the clinical application of various blood‐containing biomedical devices is the activation of the complement system induced by a foreign surface. A method of determining the hemolytic activity of human serum complement before and after contact with polymers was chosen in order to elucidate the relationship between polymer surface types and the degree of complement activation. The complement activation of each donor proved to depend both on his own complement reactivity and the type of polymer surface. The role played by each constituent was estimated using the rate constants for spontaneous (k_sp) and induced (k_ind) complement activation. The negative correlation (−0,88, p < 0,001) between the degree of irreversible adsorption of ¹³¹I‐serum albumin and relative k_ind was determined. Thus, we propose the use of k_ind for the criterion of conformation alterations of protein macromolecules induced by the adsorption/desorption processes on blood/surface interface, leading to complement activation.