The results of 57Fe Mössbauer investigations carried out on the hydrogenated compounds of Dy0.73Tb0.27Fe1.5Co0.5 are presented. A change in the temperature range of the [1 0 0]-[1 1 1] spin reorientation transition from 200-290 K in Dy0.73Tb0.27Fe1.5Co0.5 to 100-150 K in Dy0.73Tb0.27Fe1.5Co0.5H 0.5 is attributed to changes in the crystalline electric field (CEF) effects resulting from the increase in rhombohedral distortions due to the orientational ordering of hydrogen atoms in the lattice. The variations in hyperfine field and isomer shift are also discussed. © 1997 Elsevier Science Ltd.