Heparin uptake and desulphation by cultured macrophages were investigated. Histones, polyamino-acids, protamine and eosinophil-basic protein stimulated both heparin uptake and desulphation, processes found to be non-related. Poly-L-ornithine and poly-DL-lysine increased the heparin uptake by about 33-fold, and histone produced up to 7.5-fold increase in the desulphation. The same polycations inhibited heparin desulphation by macrophage extracts.