We analyzed the binding of heparinoid or heparin with fibrinogen by real-time measurement using surface plasmon resonance technology. Poly(glucosyloxyethyl methacrylate) sulfate [poly(GEMA) sulfate] and dextran sulfate were used as heparinoids. The binding ability of each sulfated polymer was estimated by having each polymer-containing buffer interact with the sensor chip surfaces that had immobilized fibrinogen. Dextran sulfate and poly(GEMA) sulfate showed high affinity to the fibrinogen in this experiment, while the heparin did not. All of the dextran sulfates were desorbed from its surface, while about 30% of the poly(GEMA) sulfate remained on the immobilized fibrinogen upon the addition of NaCl to the buffer which was done in order to analyze the desorption of poly(GEMA) sulfate or dextran sulfate from the surface of the fibrinogen. These data show that the type of binding between fibrinogen-poly(GEMA) sulfate was different from that of dextran sulfate, indicating that the interaction between fibrinogen and poly(GEMA) sulfate was caused not only by an electrostatic but also by a hydrophobic force. These results suggest that the interaction mechanism of heparinoids with fibrinogen was different from that of heparin.