A kinetic model is presented for the pyrolysis of ethylene at pressures ranging from 0.8 to 27 kPa and temperatures from 774 to 1023 K. The model is based on experimental measurements of C2H2, C2H6, C3H6, 1-C4H8, and 1,3-C4H6. In this temperature range the reaction is initiated by the disproportionation of C2H4and the observed products result from reactions of the C2H3and C2H5radicals produced in this process. The C2H2and 1,3-C4H6result from reactions of C2H3while C2H6, C3H6, and 1-C4H8result from reactions of C2H5. C2H2is produced exclusively by the decomposition of the C2H3radical. This process is in its falloff region throughout the range of experimental conditions examined and the yield of C2H2provides a measure of the degree of falloff. The production of 1,3-C4H6is controlled by the reaction C4H7–> C4H6+ H. The rate constants for this reaction were independent of pressure and are given as a function of temperature byk= 2.2 × 1013exp (-19.6 × 103/T). Production of C2H6is controlled by the reaction C2H5+ C2H4–> C2H6+ C2H3. The rate constant for this reaction is given as a function of temperature byk= 5.83 × 1011exp (-14.6 × 103/T). C3H6is produced by decomposition of 2-C4H9and is controlled kinetically by the isomerization reaction 1-C4H9–> 2-C4H9. The temperature dependence of the rate constants obtained for this reaction leads to a preexponential factor of approximately 3 × 1016and an activation energy of approximately 200 kJ mol-1. The yield of 1-C4H8is controlled by 1-C4H9–> 1-C4H8+ H. The rate constants for this reaction were independent of pressure and are given as a function of temperature byk= 2.97 × 1012exp (-17.1 × 103/T).Key words: kinetic modeling, ethylene pyr