Abstract EPR measurements on CuAl 0.99Cr 0.001O 2 have allowed the determination of the zero field splitting ( D = 0.330 cm −1). An interpretation of the exchange narrowing of EPR linewidth has been given based on the Anderson and Weiss model leading to a value of 1.8 for the C 0-constant in the expression for the exchange field: H e = C 0( Jg −1β)[S(S + 1)] 1 2 . From these results and previous data a D-value be proposed for AgCrO 2 (0.307cm −1), and compared to those for CuAlO 2 and CuCrO 2. The variation is correlated with the degree of trigonal distortion of the Cr 3+ octahedral site based on structural data. The thermal variation of the linewidth for AgCrO 2 and CuCrO 2 confirms the existence of 3D-long range antiferromagnetic ordering at temperatures close to those determined from static susceptibility measurements.