We use an ensemble Monte Carlo technique to model the thermalization of electron-hole plasmas following a laser excitation. For concreteness, we concentrate on the results of two recent experiments. Our calculations quantitatively confirm the existence of separate effective electron and hole temperatures during the first 10 ps in AlxGa1-xAs. The carrier cooling can be explained by invoking both nonequilibrium phonons and carrier degeneracy. Comparison with a band-edge luminescence experiment brings out features concerning the electron-hole and intervalley scattering contributions.