Abstract Eyes of nineteen malacostracan crustaceans (sixteen from coastal, three from deep water) have been examined for purines and pteridines, with a view to determining their role as reflecting pigments. White shrimp, Penaeus setiferus , received most attention; other animals examined were one isopod, one stomatopod, eight penaeids, six brachyurans, and two anomurans. Methods used were paper chromatography, enzymatic assay or identification, UV spectrophotometry and fluorophotometric assays. Isoxanthopterin was the chief pteridine present in eyes of white shrimp, in amounts up to 250 μg per eye; xanthopterin and 2-amino-4-hydroxypteridine occurred in smaller quantities, in that order. Isoxanthopterin was generally present in the eyes of the malacostracans examined except for the scarlet prawn, Aristaeomorpha foliacea , which had only xanthopterin. In the white shrimp, pteridines are localized in the three reflecting layers of the eyes. Purines generally occur in small amounts (except one unidentified quenching substance); they include xanthine, hypoxanthine and guanine. Eyes of mantis shrimp contain much xanthine.