Cholesteryl isobutylcarbonate, C 32H 54O 3, contains two molecules (A and B) in the asymmetric unit. The isobutylcarbonate chain of molecule A and the isoprenoid tail of molecule B are each conformationally disordered over two positions. The two distinct molecules form separate stacks along the screw axes so that they are arranged in an antiparallel array, forming monolayers with a thickness of d 001 = 19.412 A. The central regions of the monolayers are characterized by efficient molecular packing and are separated by interface regions, which are more loosely packed.