Abstract Dielectric susceptibility changes under action of external DC electric fields have been studied for lead magnesium niobate PbMg1/3Nb2/3O3 (PMN) (1,1,1) oriented crystals. At about 210 K, an anomaly appears, which depends on the strength of the field and on the measurement conditions. An attempt has been made at constructing the phase diagram in the (E,T) plane, in the range 150–400 K and 0–2.7 kV/cm. Four different phases are identified in the (E,T) range studied. We suggest that these represent a paraelectric, a glassy, a metastable ferroelectric and a ferroelectric phase. To induce the ferroelectric phase, an applied field of at least 2.25 kV/cm is required.