The magnetic phase diagram of Ho-Ag has been established using magnetoresistance, magnetostriction and neutron diffraction experiments versus applied field and temperature. Three different magnetic phases were observed: an incommensurate antiferromagnetic phase (IC) below T-N = 33 K, a commensurate antiferromagnetic phase (C) above 5 T and below T-1 (5-8 K) and a ferromagnetic component above 3 T. The IC phase undergoes spin reorientations around 5 T (IC') and 13 T (IC'').