The experimental results of the influence of bivalent (Ni2+, Co2+, Fe2+, Mn2+, Ba2+, Ca2+, Sr2+) and trivalent (Fe3+, Mn3+, Y3+, La3+) impurity ions on growth rates and Surface morphology of potassium dihydrogen phosphate (KDP) crystal faces are presented and discussed. The analysis of the obtained results is performed in conjunction with the theoretical results presented in our previous paper (Rak et al., J. Crystal Growth) concerning modelling of structure of defect centres formed in KDP crystals by these impurities. It is found that the effect of Me3+ ions is caused mainly by their adsorption on crystal faces while, in case of Me2+ impurities, the ions incorporated into surface crystal layer and the lattice stresses generated by them play a leading role in the effect of bivalent impurities on growth kinetics and surface morphology (the structural mechanism of the impurity influence-SMII). (C) 2004 Elsevier B.V. All rights reserved.