Investigations into the effects of relative molecular mass (RMM) and structure of poly(alkenoic acid)s on their adsorption on to hydroxyapatite (HAP) were carried out with a view to establishing factors that influence the adhesion of glass-poly(alkenoic acid) cements to tooth material. The effects of pH and fluoride addition were also studied. It was found that high adsorption levels were achieved under conditions of high chain entanglement, such as in a concentrated solution of a polyacid of high RMM. Theories of adsorption of carboxylic acids on to HAP are reviewed in the light of these studies and previous work at our laboratory.