Diisopropyl ether solvates of beclomethasone 17,21-dipropionate (I), useful in aerosol inhalers (formulation given), are prepd. by dissoln. of I in an org. solvent, and pptn. by addn. of diisopropyl ether (II). Thus, 100 g I in 1 L CHCl3 was filtered and treated with 4 L II under stirring for 1 h. The pptd. solid was filtered, washed with II, and dried at 35.degree. to give 104.9 g I.cntdot.II solvate, m. 210-2.degree., which lost 10.8% wt. on drying, and showed 6.9% II and 3.0% CHCl3 by gas chromatog. Solvates of I and II also contg. THF or dioxane were similarly prepd. The solvates are stable in bulk or micronized forms, with the latter showing no significant crystal growth or agglomeration in aerosol formulations (no data).