The term urobilinoids is a common delineation for the group of bilirubin hydroderivatives formed by indigenous gut microflora in the intestinal lumen. Among them, colourless chromogenes urobilinogen and stercobilinogen represent the most important species. Their coloured oxidation derivatives, urobilin and stercobilin, respectively, are responsible for characteristic colour of stools. Nomenclature of bilirubin hydroderivatives is not unified; one can often encounter various names for the same compound. The aim of this review is to survey present knowledge in this as yet not well-understood field of biochemistry, as well as to point to the correct terminology and classification of bilirubin hydroderivatives.

        Key words: bilirubin, urobilinouids, intestinal microflora, nomenclature of bilirubin hydroderivations.