Dimeric cyclotetramethylenecarbonate (TeMC)(2) was polymerized in bulk at 185 degrees C, Either nBuSnCl(3) or Sn(II)2-ethylhexanoate (SnOct(2)) were used as catalysts. SnOct(2) proved to be somewhat less reactive, but high yields (up to 93%) and high viscosities (eta(inh) up to 0.85 dL/g) were obtained with both catalysts. Viscosity-average molecular weights (M(v)) in the range of 50-75 x 10(3) were determined. The isolated crystalline poly(tetramethylene carbonate)s were characterized by IR, H-1- and C-13-NMR spectra, DSC measurements and WAXD powder pattern. CH2OH and octoate end groups were detected by means of H-1-NMR spectroscopy when SnOct(2) was used as initiator, but ether groups were absent. DSC measurements revealed that poly(tetramethylene carbonate) is a slowly crystallizing polymer with a degree of crystallinity below 50% and a melting temperature in the range of 64-69 degrees C depending on the molecular weight. Thermogravimetric analyses proved that polyTeMC decomposes completely between 240 and 340 degrees C without leaving a residue. CO2 and tetrahydrofuran were the main degradation products.