The interactions between low (MG2) and high (MG1) molecular-weight human submandibular-sublingual mucin and hydroxyapatite (OHAp) were compared using a quantitative assay. Data obtained appeared to empirically fit the Langmuir adsorption isotherm. Apparent affinity constants derived from this isotherm indicated that MG1 had a greater affinity for OHAp than did MG2. Inhibition studies revealed that salivary glycolipids inhibited the interaction of MG1 and OHAp without influencing MG2 adsorption. In contrast, MG2 adsorption to OHAp was markedly inhibited by cysteine-containing salivary phosphoprotein fractions. Collectively, the data indicate MG1 and MG2 differ in their interaction with OHAp.