Azo dyes of the formula ##STR1## where L.sup.1 is hydrogen, C.sub.1 -C.sub.8 -alkyl or phenyl,L.sup.2 and L.sup.3 are each substituted or unsubstituted C.sub.1 -C.sub.8 -alkyl, or together a radical of the formula ##STR2## where n is 0, 1 or 2, Y.sup.1 and Y.sup.4 are hydrogen, hydroxymethyl, 1,2-dihydroxyethyl or a radical of the formula COO.sym.M.sup..crclbar. or SO.sub.3.sup..crclbar. M.sup..sym., Y.sup.2 and Y.sup.3 are halogen or hydroxymethyl, and M.sup..sym. is the equivalent of a cation,L.sup.4 is hydrogen, substituted or unsubstituted C.sub.1 -C.sub.8 -alkyl, substituted or unsubstituted phenyl, halogen, C.sub.1 -C.sub.8 -alkoxy, substituted or unsubstituted phenoxy, C.sub.1 -C.sub.8 -alkylthio, C.sub.1 -C.sub.8 -alkylsulfonyl, substituted or unsubstituted phenylthio, substituted or unsubstituted phenylsulfonyl, C.sub.1 -C.sub.8 -alkoxycarbonyl, C.sub.3 -C.sub.6 -alkenyloxycarbonyl or phenoxycarbonyl,X is nitrogen or the radical C--L.sup.5, where L.sup.5 is as defined in the specification,K is the radical of a coupling component, andnovel crystal forms of thienylazobenzene dyes are useful for dyeing or printing textile materials.