Urethane reactions of cycloaliphatic and aromatic diisocyanates with hydroxy-terminated fluoropolyethers (FPEs) of various molecular weights and structure, at NCO : OH = 2, have been studied by monitoring, by IR analysis, the rate of decrease in NCO absorbance at 2264-2268 cm(-1). Different diisocyanates have been tested, among them the following: 4,4＇-dicyclohexylmethane diisocyanate (H12MDI); 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate (IPDI); 2,4-toluene diisocyanate (TDI). Ethyl acetate (EA), methyl isobutyl ketone (MIBK), and hexafluoroxylene (HFX) have been used as solvents in presence of dibutyltin dilaurate (DBTDL) or 1,4-diazabicyclo [2.2.2]octane (DABCO) as catalysts. These reactions gave rise to NCO-end-capped FPE-oligourethanes. Preliminary solubility tests for HO-terminated FPEs in various solvents made it possible to select proper candidates for carrying out reaction in homogeneous conditions at high concentrations of reagents (30-50% w/w). The second-order kinetic mechanism was shown to be valid. Positive deviations from linearity for the second-order kinetics around 40-80% conversion, found for most of the FPE diols, were attributed to the autocatalysis of the isocyanate-hydroxyl reaction by the arising urethane groups. Uncatalyzed reactions with cycloaliphatic diisocyanates are very slow at 40 degrees C. The tertiary amine DABCO is a much less effective catalyst than DBTDL. FPEs having terminal OH groups separated from the perfluorinated main molecular chain by -(OCH2CH2)(n)- segments (n = 1-2) are generally more reactive than FPEs with end -CH2OH groups.