In this study, a series of potassium- and carbonate-containing apatites is prepared by solid state reactions at high temperature in a nearly dry CO2 atmosphere. Chemical and physical analyses showed that the samples are single-phase and contain 4-12 wt % carbonate. Their stoichiometry conforms to Ca10-xKx[(PO4)(6-x)(CO3)(x)][(OH)(2-2y)(CO3)(y)] with 0 < x < 1 and 0.7 < y < 0.9 as the result of the substitution of PO43- as well as of OH- by CO32- in the apatite lattice according to the mechanisms [Ca2+ + PO43- <----> K+ + CO32-] and [2OH(-) <----> CO32- + V-OH], where V-OH stands for a vacancy in the OH- sublattice. Although these mechanisms appear to occur independently of each other, they have a marked effect on the IR characteristics of the solid.