The graphic method of analysis for identification of internal symmetry centres in amino acid sequences (AAS) of insulin receptor (IR) cytoplasmic 'tail' was used. The method was based on the comparison of normal and conversional sequences (AAS or sequences of amino acid codon roots). It was shown, that the regions of IR cytoplasmic domains most important for receptor functional activity possess symmetrical structure. The regions participate in the autophosphorylation, tyrosine kinase activity, ATP-binding, interaction with different types of G-proteins, processing of receptor molecule, etc. The functionally important amino acids and their clusters either were included in the formation of the internal symmetry centres or were localized close to them.