We have studied the effects of polyunsaturated fatty acid (PUFA) supplementation in utero and throughout life in mnd mutant mice, a proposed model for juvenile neuronal ceroid lipofuscinosis (CLN-3). Unlike our earlier in-vitro studies in humans with CLN-3, and in-vitro studies in CLN-3 lymphoblasts, we saw no beneficial effects in electroretinographic, electron microscopic or clinical studies in the mnd mice. Electron microscopy of brain revealed a pattern which was not consistent with the characteristic ceroid patterns in CLN-3. Our data suggest that the mnd mouse is not responsive to PUFA supplementation and may not be an appropriate animal model for CLN-3.