Halogen-free flameproofed thermoplastic molding materials based on polyphenylene ethers and polystyrene containing, as essential components,A) from 5 to 92% by weight of one or more polyphenylene ethers,B) from 5 to 92% by weight of a vinylaromatic polymer andC) from 3 to 25% by weight of a flameproofing agent based onC1) from 20 to 100% by weight (based on the total amount of C) of a polymeric phosphorus compound which is obtained by polymerizing or copolymerizing one or more compounds of the following structure: ##STR1## where ##STR2## R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.10 and R.sup.11 are each hydrogen, alkyl, cycloalkyl, aralkyl or aryl,R.sup.7, R.sup.8 and R.sup.9 are each alkylidene, cycloalkylidene, aralkylidene or arylidene,m, p, q, r, s, t, u and v are each 0 or 1,n is 0, 1 or 2,U is COO, O, S or NR.sup.9,V, W, X and Y are each O, S or NR.sup.9 andZ is O, S or NR.sup.10 R.sup.11, andC2) from 0 to 80% by weight (based on the total amount of C) of a low molecular weight phosphorus compound selected from the group consisting of the phosphine oxides, phosphates, phosphinic acids and salts and esters thereof, phosphonic acids and salts and esters thereof and red phosphorus.