The alloys ErPrFe17-xGax and ErPrFe17-xSix (x = 0-3.5) have been prepared and their structure and magnetization have been investigated. Powder X-ray diffraction patterns show that these compounds crystallize in hexagonal Th2Ni17 (2:17) structure. The lattice parameters are found to increase as the Ga concentration is increased and decrease with increase of Si concentration. The saturation magnetization (Ms) measured at 20 K is found to increase initially and then decrease as the Ga and Si concentration are increased beyond 0.1. The Curie temperatures of ErPrFe15Ga3.5 and ErPrFe15Si3.5 are 528 and 537 K which are 241 and 250 K, respectively, higher than that of the parent compound ErPrFe17 and this has been explained on the basis of band model. The X-ray diffraction patterns taken for the magnetically aligned samples suggest that the easy magnetization direction (EMD) is in the basal plane in the Si substituted samples whereas in the case of the Ga substituted samples the EMD tend to be away from the basal plane. The anisotropy fields (HA) calculated from the magnetization measurements on aligned samples show that in the case of the Ga substituted compounds there is a significant increase in HA compared to the ones that are seen in the Si substituted compounds. © 2002 Elsevier Science B.V. All rights reserved.