The influence of inhibitors of varying functional groups on the crystal growth of calcium phosphate dihydrate (CaHP04.2H20, DCPD) on DCPD seed crystals at pH 6.00,37"C, has been studied using the constant composition technique. The inhibitors studied include: (a) polyphosphate (sodium pyrophosphate, sodium hexametaphosphate, SHMP), (b) phosphonates (nitrilotris(methy1ene phosphonic acid), NTMP; I-hydroxyethylidene-1,l-diphosphonic acid, HEDP; ethylenediaminetetra (methylene phosphonic acid), ETMP; hexamethylenediaminetetra(methy1ene phosphonic acid), HMDP); and (c) myoinositol hexaphosphoric acid (phytic acid). The effect of these inhibitors on the growth kinetics have been studied at several inhibitor concentrations. The retarding effect of these inhibitors is discussed in relation to calcium-inhibitor complex formation on the DCPD seed crystals and the structural features of the inhibitor molecules. The fit of the Langmuir adsorption to experimental data supports a mechanism of inhibition through molecular adsorption of the inhibitor ions on the surface of growing crystals. Based upon the kinetic data, the overall order of inhibitors effectiveness is ETMP > HMDP > phytic acid > hexametaphosphate > HEDP > pyrophosphate ZAHID AMJAD. Can. J. Chem. 66, 2181 (1988. OpCrant a un pH de 6,0, i une tempkrature de 37°C et utilisant la technique de la composition constante, on a CtudiC l'influence des inhibiteurs portant divers groupements fonctionnels sur la croissance cristaux de phosphate de calcium dihydrate (CaHP04.2H20, DCPD) sur des cristaux de DCPD ensemences. Les inhibiteurs examinks comportent; (a) des polyphosphates (pyrophosphate de sodium, hexamCtaphosphate de sodium, HMPS), (b) des phosphonates (nitrilotris(acide methylkne phosphonique), NTMP; acide hydroxy-1 tthylidkne diphosphonique-1,1, HEDP; Cthyl&nediaminetCtra(acide mCthylkne phosphonique), HMDP; et (c) l'acide hexaphosphorique du myoinositol (acide phytique). On a CtudiC l'effet de ces inhibiteurs sur la cinCtique de la croissance i plusieurs concentrations d'inhibiteurs. On discute de l'effet retardant de ces inhibiteurs en