A class of steroidal compounds classified as bile acids is produced naturally from cholesterol in liver. Apart from their biological importance some representatives of this class show interesting properties in their crystal form. Cholic acid (CA, Fig. 1) is amongst the best studied1. Due to its unique amphiphilic form cholic acid is suitable compound in forming crystal host frameworks that can include various guest molecules. Cholic acid is characterized by four chained rings which form rigid body of the molecule. Three OH groups on one side and two methyl groups on the opposite side are responsible for facial amphiphilicity of the molecule. This property is responsible for dominant mode of packing in majority of its crystal structures: the hydrophobic faces of the molecules join to make bilayers with hydrophobic surfaces. The crystal packing is realised through stacking of such bilayers. Because of the shape of CA molecules (Fig 2.), such an assembly leaves open cavities on the hydrophobic interfaces between the bilayers. Various host-guest crystals of CA are based on inclusion of molecules of appropriate size into these cavities. Although guest molecules show marked variation in their chemical nature and size, some of the characteristics of the crystal packing of CA remain surprisingly uniform. For example, the b axis of many crystals is close to 8 Å and the space group is P 21. This is also the case for four compounds of CA with alkylammonium (CH3-(CH2)n-NH3+ of varying chain length from n=9 to 15). To study packing arrangements of CA host-guest compounds a comprehensive survey is made in the latest version of CSD (version 5.27)2 database with particular emphasis on these parameters. This attractive research subject is reflected in the fact that in the most recent update of the CSD alone there are 58 structures of this kind!