The present invention relates to disperse azo dyes of formula wherein R1 is bromo, nitro, cyano, methyl, methoxy or trifluoromethyl; R2 is hydrogen, chloro, bromo or trifluoromethyl; R3 is hydrogen, chloro, bromo, methoxy, trifluoromethyl, nitro or cyano; and R4 is methyl, ethyl, n-propyl, 2-methoxyethyl, methoxycarbonylmethyl or 2-methoxycarbonylethyl; with the proviso that R1 is cyano in case R2 denotes chloro or bromo, to a process for the preparation of such dyes and to their use in the dyeing or printing of semi-synthetic and, especially, synthetic hydrophobic fibre materials, more especially textile materials.