[en] Quantitative Mn, Si, Cr, and Fe profiles have been obtained by secondary ion mass spectrometry on Cr-doped semi-insulating GaAs subjected to unencapsulated anneals at 750 ⁰C in a hydrogen ambient. The chemical concentration of Mn induced by annealing is greater than can be realized by diffusion from the bulk (Mn=3 x 10¹³ cm^-3), and relates directly to both the free-hole concentration measured in the conducting surface layer and the 5 K photoluminescence (PL) intensity of the zero-phonon emission at 1.409 eV. Post anneal profiles of the elements Si and Cr, which are present in the bulk prior to annealing, indicate that Si remains uniformly distributed while Cr suffers out-diffusion in conjunction with surface accumulation. The distribution of Fe which peaks at 5 x 10¹⁵ atoms cm^-3 may, like Mn, arise from incorporation from the annealing ambient