EPR in the excited Γ5(2) triplet state of Tm3+ in cubic TmP has been studied. From the temperature dependence of the g‐value, it was found that the fourth‐order term dominates in the crystal‐field, and the exchange interaction between Tm3+ ions is weakly antiferromagnetic. The most striking feature of the observed behavior is the presence of an anomalous maximum in the g‐factor temperature dependence occurring at about 40K, where the intensity and line widths also have maxima. Analysis of the EPR intensity gives the separation between the excited Γ5(2) state and the singlet Γ1 ground state as about 60K. Brief mention is made of the results of EPR observations in the excited Γ5 level of Pr3+ in PrP and for Gd3+ as a dilute impurity in TmVA and PrVA (VA=P, As, Sb, Bi).