The aim of this research was the investigation of the properties of aziridinyl azo disperse dyes with respect to their synthesis. The cyclisation of the precursor to the corresponding aziridinyl azo dyes from N-$eta$-methanesulphonylethylaniline azo dyes directly without replacement by a bromine atom gave excellent yields of aziridinyl azo compounds. The azo disperse dyes containing terminal aziridinyl rings were characterised using Inr/VIS spectroscopy, $^1H$-NMR. It was found that the dyes absorbed hypsochromically in comparison with similar dyes that contained terminal hydroxyethyl groups (hydrolyses form of the aziridinyl azo dyes). A singlet peak for the aziridinyl ring of chemical shift ($delta$) 2.2 was observed by NMR spectroscopy.