PURPOSE: To obtain an azo compound, an intermediate for ultraviolet light absorbers, in high yield, by reacting a 2,4-dialkylphenol with an o-nitroaniline diazo compound in an oil-in-water type dispersion, using a specific surfactant.

CONSTITUTION: A 2,4-dialkylphenol of formula I (R1 and R2 are 1W8C alkyl groups) is dissolved in a water-immiscible organic solvent and emulsified with Turkey red oil and water to give an emulsion, which is then reacted with a diazo compound of an aqueous solution of an o-nitroaniline of formula II (R3 is H or halogen) in the presence of an anionic or nonionic surfactant, e.g. polyoxyethylene- alkyl phenyl ether sulfate, in an oil-in-water type dispersion to form an azo compound (C) of formula III. Ultraviolet light absorbers of formula IV can be obtained from the resulting compound (C).