The model problem of a gas confined between stationary heated plates is analyzed numerically to quantify slip effects for gas densities ranging from near‐continuum to highly rarefied conditions. Calculations are performed with the direct simulation Monte Carlo technique using two gas–surface interaction models and with a finite‐difference Navier–Stokes method using slip boundary conditions. Comparisons are made with experimental density profiles and with previous discrete ordinate calculations using a model form of the Boltzmann equation. To the resolution of the experimental data, both direct simulation Monte Carlo and the Navier–Stokes equations with slip provide very good agreement for essentially all cases considered, while the discrete ordinate results are less accurate. The calculated pressure and temperature profiles show slightly larger differences. The details of the gas–surface interaction model have a relatively small effect on calculated density profiles. The direct simulation Monte Carlo and no‐slip Navier–Stokes results are found to agree quantitatively for all properties at very small Knudsen number [O(10−3)]. Detailed direct simulation Monte Carlo quantities near the plates are used to quantify discrepancies in the continuum slip models and suggest possible improvements.