MCNP applies only nuclear data tabulated at specific temperatures and does not incorporate methods for general temperature interpolation of nuclear data. However, in models representing realistic power reactor cores, it is generally necessary to represent the distribution of fuel and coolant temperatures to reliably predict detailed power distributions and reactivity feedback effects. This paper describes methods that can be easily applied for the representation of cross-section data at general temperatures, based on interpolation through mixing of nuclide representations at multiple temperatures. The discrepancies due to the interpolations have been determined to be insignificant relative to the estimated uncertainties in typical calculated eigenvalues.