The crystal structures of two forms of alclometasone dipropionate have been solved and refined using a single synchrotron X-ray powder diffraction pattern and optimized using density functional techniques. Both forms crystallize in the space group P212121 (#19) with Z = 4. The lattice parameters of Form 1 are a = 10.44805(7), b = 14.68762(8), c = 17.31713(9) Å, and V = 2657.44(2) Å3, and those of Form 2 are a = 10.69019(13), b = 14.66136(23), c = 17.17602(23) Å, and V = 2692.05(5) Å3. Both density functional theory and molecular mechanics optimizations indicate that Form 2 is lower in energy, but the differences are within the expected uncertainties of such calculations. In both forms, the only traditional hydrogen bond is between the hydroxyl group and the ketone in the steroid A ring. The chlorine atom acts as an acceptor in two intramolecular C–H⋯Cl hydrogen bonds involving ring hydrogens, as well as in an intermolecular hydrogen bond involving a methyl group. There are several C–H⋯O hydrogen bonds, mainly to ketone oxygens, but also to the hydroxyl group and an ether oxygen. The powder patterns have been submitted to ICDD for inclusion in the Powder Diffraction File™.