The reactions of 6-aminouracil with ethylene carbor ate were investigated. Potassium carbonate or I.,4-diazabicyclo[2.2.2] octane was used as a catalyst. An excess of ethylene carbonate was applied in the syntheses. In this way, polyetherols with 1,3-pyrimidine rings in their structure were prepared. The structure of the products was analyzed with infrared, proton nuclear magnetic resonance, and matrix-assisted laser desorption /ionization time-of-flight techniques. Some physical properties and the thermal stability of the prepared polyetherols were investigated.