The　nucleation　of　KDP　and　DKDP　crystals　from　aqueous　solutions　was　studied　in　the　presence　of　alcoholic　additives.　Induction　periods　for　nucleation　as　a　function　of　supersaturation　in　different　alcoholic　additives　were　measured.　The　surface　free　energy,　Gibbs　free　energy　and　radius　of　the　critical　nuclei　of　KDP　and　DKDP　crystals　were　calculated　in　terms　of　the　classical　nucleation　theory.　In　the　presence　of　alcoholic　additives,　the　effect　of　additives　on　nucleation　of　KDP　and　DKDP　crystals　growth　solutions　are　discussed.