Oligosaccharide heparin fragments as inhibitors of complement cascade

There is disclosed oligosaccharide compounds having heparin-like anticomplement activity and reduced anticoagulant activity as compared with heparin on a weight or molar basis. The oligosaccharide compounds have at least 5 and no greater than 25 saccharide units. The oligosaccharides can have an even nuber of saccharide units with a terminus nonreducing sugar, or an odd number of saccharide units without a terminus nonreducing sugar. There is also disclosed anticomplement pharmaceutical compositions with reduced anticoagulant side effect activity and a process for preparing the oligosaccharide compounds.