The aspiration efficiency of a thin-walled, shallow-tapered aerosol sampler, as studied by Vincent et al. (1986, J. Aerosol Sci. 17, 211-224), which is rear-facing the wind is numerically investigated. The turbulent fluid flow is predicted by employing the control volume, finite-difference method with a body-fitted coordinate system and a low Reynolds number k-epsilon turbulence model. The particle trajectories are calculated by integrating the particle equations of motion using either the turbulent instantaneous fluid velocity (a stochastic model) or the mean fluid motion (the mean motion model). The aspiration efficiency for thin-walled, shallow-tapered samplers which rear-face the wind as predicted by the two models, are in good agreement and although the results show an unusual behaviour they agree reasonably well with all the available experimental data.