Abstract Biologically uncommon d-aspartyl residues have been reported in proteins of various elderly tissues. We prepared a polyclonal antibody against d-β-Asp-containing peptide and examined its immunoreactivity in the skin. The antibody recognized integrated or disintegrated elastic fibers in the sun-exposed skin but not in the sun-protected skin of the elderly donors. Western blot analysis of the proteins isolated from sun-damaged skin demonstrated that the 50 kDa protein was immunoreactive with both antibodies for d-β-Asp-containing peptide and elastin. Ultraviolet (UV) irradiation on normal skin caused the appearance of d-β-Asp-containing peptide-immunoreactive fibers in the dermis. These results suggest that UV irradiation is closely related to the formation of d-β-Asp in the elastic fibers of skin. We propose that the antibody could be a useful indicator for sun damage of the skin.