A. method of preparing; a fiber-forming linear polyester which comprises. heating until thickened a; mixture. comprising, (a) a. member of the group consisting oi stilhene. di'carboxy lic acid, its esters and its acid chlorides'a'i'id' (b) a polyoxyalkylene glycol of the formula where R: is an alkylene radical of from about 2 to fi carbon atoms and n is an integer of from about 2 to 5. 15'.