The relaxation of the ion distribution function was measured for a plasma (n ≃ 1012 cm−3, Ēi = 200 eV) confined in a circularized, stabilized magnetic mirror well. The results were compared with the predictions of a Fokker-Planck computer code. The evolution of an initially skewed angular distribution function appeared to be in good accord with the theoretical model. However, the final anisotropy of the plasma was greater than the calculated one.