"The hydrocarbon evolution data of Richardson et al. (1982) is reanalyzed to determine improved rate expressions for oil generation from Colorado oil shale under rapid pyrolysis conditions. Contributions from low molecular weight gases are subtracted from flame ionization detector data to obtain the rate of oil generation alone. Equally good fits to the data were obtained using two parallel first-order reactions or a single reaction with an effective reaction order of 1.51. The latter expression is easier to incorporate into global process models. The rate expressions are independent of shale source (Anvil Points or Tract C-a) and particle size (0.5 to 2.4 mm). The kinetic data are consistent with the previous conclusion that the small incremental oil yield possible for fluidized-bed pyrolysis requires a longer residence time than that estimated by kinetic expressions derived from slow heating rate data."