EPR measurements of the A 6 V 6 P 6 P 3 1 (A = K, Rb, Tl) systems at 300, 77 and 4.2 K have been carried out. Negative g-shift is observed in all cases. The g i s o values in the systems do not change significantly in the temperature range 4.2-300 K. Unresolved EPR lineshapes are observed in all cases owing to the delocalization of the vanadium 3d 1 electron in the host lattice. Because of the similar effective ionic radii of the Rb + and Tl + ions, which are bigger than that of the K + ion, these ions compress the octahedral VO 6 units and the pyramidal VO 5 units having the V 4 + sites to the same extent. Thus in the case of the Rb + and Tl + ions, the observed g i s o values are similar. The magnetic susceptibility plots show that these systems exhibit antiferromagnetic behaviour, with the Neel temperature around 50 K in all cases.