The present invention relates to azo dyes of formula (1), wherein R1 denotes C1-C12alkyl which is unsubstituted or substituted by one or more C1-C12alkoxy groups, hydroxyl groups, amino groups, cyano groups or halogen atoms and which may be interrupted one or more times by the radical —O—, —S—, —COO— or —OOC—: R4 is hydrogen or C1-C12alkyl; either R2 is cyano and R3 is halogen or R2 is halogen and R3 is cyano; and Ar represents a carbocyclic or heterocyclic aromatic radical, to the process for the preparation thereof, to mixtures containing said dyes and to the use thereof in dyeing or printing semi-synthetic and especially synthetic hydrophobic fiber materials, more especially textile materials.