We know that many familiar objects such as gloves, shoes and screws are non identical with their mirror images. The same applies to certain chemical compounds. These compounds show a degree of asymmetry in their structure which means that when looked at in a mirror, their images are not superimposable – they are chiral compounds and have two forms (enantiomers). Until recently biochemists have only been concerned with perhaps one form, other forms having been ignored primarily due to analytical difficulties. We now know of inborn errors of metabolism where one form of a pathological metabolite predominates, thus requiring precise enantiomeric analysis. This article provides a background to the field of enantiomers and their analysis as demonstrated by examples of inborn errors of metabolism and hints at the possible discovery of as yet unidentified metabolic pathways. Conclusion Recent advances in the field of enantiomeric metabolite analysis, in particular the use of enantioselective gas chromatography- mass spectrometry, have an increasingly important role to play, not only in the diagnosis of inborn errors of metabolism, but also to increase our understanding of normal physiological processes.