Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used to examine the adsorption behaviour of bovine serum albumin (BSA) and bovine fibrinogen on ultra-pure titanium, (up)Ti, commercially pure titanium, (cp)Ti, and Ti-6Al-4V electrodes at 310 K (37°C) and 316 K (43°C) in a phosphate buffer of pH 7.4. Surface charge density measurements were obtained from cyclic voltammetry. The impedance spectra were interpreted in terms of an equivalent electrical circuit (EEC) based on a possible physical model, with the circuit elements representing the electrochemical properties of the investigated system. The adsorption of BSA and bovine fibrinogen onto the titanium surfaces resulted in an increase in surface charge density and capacitance. Three trends were observed with both cyclic voltammetry and EIS: the adsorption of fibrinogen was greater than that of BSA on all three surfaces, the adsorption of both proteins was greater at 310 K (37°C) than 316 K (43°C) on all three surfaces, and the adsorption of BSA and fibrinogen at both temperatures increased with increasing titanium composition of the electrode, (up)Ti > (cp)Ti > Ti-6Al-4V. Two different techniques were used to calculate the surface concentration, [, from the cyclic voltammetry measurements. One calculated the surface concentration from the plateau values of the plots of surface charge density versus the bulk protein concentration. The other used the slope from the initial adsorption behaviour to calculate the maximum surface concentration from Langmuir adsorption isotherms. Langmuir adsorption isotherms were also used to obtain the Gibbs free energy of adsorption of BSA and fibrinogen on each surface. The results indicate that very strong adsorption of both proteins occurred accompanied by a charge transfer mechanism involving chemisorption. An adsorption mechanism was proposed for the interaction of the positively charged amino groups on the basic amino acids of the proteins with the titanium surfaces at cathodic potentials. These electrochemical methods were shown to be a valuable tool in studying the interaction of proteins with these biomaterials.