The constant composition technique has been used to study the influence of polymeric additives on the kinetics of crystal growth of hydroxyapatite, HAP, at pH = 7.40, 37°C, and at low supersaturation. The polymeric additives investigated include: Polyacrylic acid, PAA, ( MW 800--50,000); Polyacrylamide, PAM; Poly (2-acrylamido-2-methyl propane sulfonic acid), PSA; and Poly (diallyldimethyl ammonium chloride), PDADMAC. The effect of these additives has been studied at several additive concentrations. It has been found that addition of low levels of PM of low molecular weight to the calcium phosphate supersaturated solution will markedly retard the rates of crystallization of HAP and the fractional reduction in rate constant can be interpreted in terms of the blocking of active growth sites through the adsorption of the PAA ions at the crystal surface. The kinetic data in the presence of PAA suggest optimum performance with an ~ 2,000 molecular weight. Based upon the kinetic data, the order of additive effectiveness is as follows: PAA >> PSA > PAM = PDADMAC = control (no polymer).