Results from simulations of the response of a methane gas sensor using optical correlation spectroscopy (CoSp) are presented. Predictions of the sensor response, signal/noise performance and detection sensitivity are made for a typical fibre optic-coupled system . Spectral absorption data of the gases is obtained from the publicly available HITRAN database. Emphasis is placed on the effects on the detection sensitivity of varying (a)the optical filter characteristics, i.e. center wavelength and bandwidth, and (b)the concentration (partial pressure) of CH, a theoretical noise-limited detection limit below 1 ppm is predicted. The cross-sensitivity to water vapor is derived and compared to that which would occur with a conventional broadband absorption method, i.e. one that would not exhibit the same selectivity as the CoSp method. This work is! impor tant for predicting the responsivity, sensitivity and crosstalk performance of practical CoSp gas detection systems.