Effective network analysis of protein data requires high-quality proteomic datasets. Here, we report a near doubling in coverage of the C. elegans adult proteome, identifying >11,000 proteins in total with 9,400 proteins reproducibly detected in three biological replicates. Using quantitative mass spectrometry, weidentify proteinswhose abundances vary with aging, revealing a concerted downregulation of proteins involved in specific metabolic pathways and cellular stress responses with advancing age. Among these are 30 peroxisomal proteins, including the PRX-5/PEX5 import protein. Functional experiments confirm that protein import into the peroxisome is compromised in vivo in old animals. We also studied the behavior of the set of age-variant proteins in chronologically age-matched, long-lived daf-2 insulin/IGF-1-pathway mutants. Unexpectedly, the levels of many of these age-variant proteins did not scale with extended lifespan. This indicates that, despite their youthful appearance and extended lifespans, not all aspects of aging are reset in these daf-2 mutants.