Mutations in mev-1 of the nematode Caenorhabditis elegans render animals hypersensitive to high oxygen concentrations. They also reduce life span. To further understand the effects of mev-1 on aging, accumulation of fluorescent material resembling lipofuscin was measured by biochemical and histological analyses. Fluorescent material accumulated in both wild type and mev-1 animals with increasing age. The mev-1 mutant accumulated more fluorescent material at a greater rate than dose wild type. Furthermore, the accumulation rates depended on concentration of oxygen. Since this phenotype has been widely used as an aging marker, these results validate mev-1's use as a model to study aging.