The thermal properties of poly(esters) containing silicon or germanium in the main chain and derived from the diphenols bis(4-hydroxyphenyl)-diphenylsilane and bis(4-hydroxyphenyl)-diphenylgermane and isophthaloyl or terephthaloyl acid dichlorides were studied by differential scanning calorimetry and dynamic thermogravimetry. Poly(esters) derived from terephthalic acid showed higher Tg and thermal stability values than those derived from isophthalic acid. Poly(esters) containing Ge showed higher Tg values but lower thermal decomposition temperatures when compared with the analogous with Si