The interaction of monoazo compounds lumogallion (LG) and magnezon HS (MHS) with cetylamine (CA) in a wide pH range has been studied using a spectrophotometric method.It has been shown that the formation of ionic associates of CA under the interaction of its cation with sulfo group of azo compounds in the pH range 1–4 does not change the electronic absorption spectra of the azodyes.