FIELD : medicine.SUBSTANCE : invention relates to the medicinal use of miglustat, namely N-butyl-1, 5-dideoxy-1, 5-imino-D-glucitol in crystalline form I, characterized by the XRPD spectrum shown in FIG. 3, in which the most intense peaks (expressed in 2θ°) must be detected at 9.93, 11.82, 14.46, 15.84, 16.41, 17.76, 17.94, 19.41, 20.01, 20.79, 21.21, 22.14, 22.62, 23.40, 24.75, 26, 04 and 30.27?±?0.2° at 2θ; and the DSC thermogram shown in FIG. 4, which has an endothermic peak at 129–130?°C, as well as its production method by debenzylation of 2, 3, 4, 6-tetra-O-benzyl-D-glucitol followed by crystallization in C1-C5 alkanol adding C3-C7 ketone with cooling the mixture and extracting solids.EFFECT : proposed a new crystalline form of valuable compounds and pharmaceutical compositions based on it, effective for the treatment of Gaucher disease.7 cl, 5 ex, 4 dwg