It is generally accepted that the specific, energetically preferred conformation of a compound decides on the nature of interactions with pharmacological receptor. Therefore it is of basic importance to get an insight into such molecular parameters as charge distribution, most preferred conformations or the distances between specified points within a molecule. The structure of some 3-amino-2-oxazolidinone derivatives with the aid of NMR spectroscopy (13C and 15N) and X-ray analysis was investigated. Analysis of AS-8 structure revealed that the crystals of hydrochloride salt are built up of cation-anion pairs and crystallized with molecule of water. The results allowed to identify the primary place of the molecule interaction with an acid residue within putative receptor site.