PROBLEM TO BE SOLVED: To provide a stable polymorph of darunavir which is crystalline, stable, non-hygroscopic in nature and free from other pseudopolymorphs or solvates, and a process for its production.SOLUTION: There is provided a crystalline darunavir hydrate substantially free of any non-aqueous solvent. Also provided is a process for producing a crystalline form of darunavir (Form C) which is a hydrate having an X-ray diffraction pattern of the figure 1, the process comprising: stirring darunavir represented by the formula (I) having at least one non-aqueous solvent in the crystal lattice, in a mixture of water miscible solvent and water； then filtering the mixture to obtain a solid； stirring the solid in water； filtering the solid/water mixture； and drying it.SELECTED DRAWING: Figure 1【課題】他の擬多形又は溶媒和物を含まない、本質的に結晶性、安定、非吸湿性であるダルナビルの安定な多形、及びその製造方法の提供。【解決手段】実質的に非水溶性溶媒を含まない結晶性ダルナビル水和物と、結晶格子中に少なくとも1の非水性溶媒を有する式（Ｉ）で表されるダルナビルを水混和性溶媒と水との混合液中で撹拌すること、次いで、該混合液をろ過して固形物を得ること、該固形物を水中で撹拌すること、該固形物/水混合物をろ過すること、及び乾燥させる図１のＸ線回折パターンを有する水和物である結晶形態（形態Ｃ）のダルナビルの製造方法。【選択図】図１
