Crystals of deuterated ammonium dehydrogen phosphate (DADP) were prepared by three times recrystallization qand distillation from ADP-D2O solution. The clear transparent crystals of DADP with a dimension of 22 x 23 x 78 mm(3) have been grown by cooling solution method. The crystal structure and the transmission spectrum are determined. (C) 2002 Published by Elsevier Science B.V.