Previous studies have shown that fluoride affected the formation of apatite in spontaneous precipitations from unstable calcium phosphate solutions partly through its effect on the stability of such nonapatitic precursors as octacalcium phosphate, Ca8H2(PO4)6.5 H2O. The present study shows that fluoride had a comparable effect on the seeded growth of apatite from stable solutions when the degree of solution supersaturation favored the transient development of octacalcium phosphate precursors on the seed surface.