The present invention is directed to a hair dyeing composition comprising at least one azo dye of the following general formula (1): A--N=N--B (1) where A=monovalent, optionally substituted heterocyclic group binding via the carbon atom to the azo group, that does not contain carboxy (--CO.sub.2H) or sulfo groups (SO.sub.3H) or quaternary ammonium groups and B=heterocyclic, aromatic or alkyl group containing a dissociative proton and, which is free of carboxy (--CO.sub.2H) or sulfo groups (--SO.sub.3H) or quaternary ammonium groups. Additionally, the present invention describes a method of dyeing human or animal hair by using such a dye and the use of this direct azo dye for dyeing human or animal hair. The use of this direct azo dye can impart the hair with an extremely vivid colour and has a less colour fade over the time.