Mucin is the main salivary protein in the mouth of animals including man. The present study aims at investigating the role of electrostatic interactions in the adsorption of mucin to titanium in vitro. The binding profile of mucin to titanium was analyzed according to an adsorption isotherm. Mucin was dissolved and the solution suspended with native, calcium, magnesium, or potassium treated commercially pure Ti powder, at pH 3.0 and 7.4. The amount of unabsorbed protein in the supernatant fluid was measured. The maximum amount of adsorbed mucin was 0.11 mg/1.0 g of Ti. The mucin-Ti association constant was estimated to be 2.91 ml/mg. Pretreatment of Ti with calcium, or magnesium alone, or combined resulted in increased adsorption of mucin to Ti. No increase in adsorption was recorded following pretreatment of Ti with potassium. The results indicate the involvement of electrostatic interactions in the absorption of mucin to Ti.