The effect of magnesium and zinc on the growth kinetics of a hydroxyapatite (0001) face in pseudophysiological solutions was investigated. The growth rates of the (0001) face were measured under various concentrations of magnesium or zinc using Moire phase shift interferometry coupled with surface observation by atomic force microscopy. The (0001) face grew not in a spiral growth mode but in a multiple two-dimensional nucleation growth mode. It was shown that the lateral growth of two-dimensional islands on the (0001) face was inhibited by the addition of magnesium or zinc, following an inhibition of the normal growth rate of the face. Although both cations inhibited growth, zinc was found to reduce the growth rate about 1000 times more effectively than magnesium.