Titanium oxide aqueous suspensions have been destabilized by a novel mechanism; the nucleation of octacalcium phosphate on the particle surfaces, using the constant composition technique. The results suggest that the potential energies resulting from the electric double layers around the titania particles play only secondary roles in the flocculation, in that a decrease inζ-potential of titania colloids from −47 mV to −13 mV does not in itself cause the titania suipension to flocculate, in contrast to the predictions of the classical DLVO theory. However, in the process of hucleation of the moderately hydrophobic octacalcium phosphate phase (γ-sequals;19.7 mJ m-2) onto titania particle surfaces, the latter become more hydrophobic with values ranging from 52 to 23.4 mJ m-2, This change is sufficient to cause the particles to flocculate since the energies of attraction result from hydrophobic interactions (90%) and van der Waals forces (10%).