The UV-irradiated, 3'-end-labeled, 92-base-pair terminus of the human alphoid sequence was incubated with purified endonuclease v. Previously unreported photoproducts were incised at purine loci. These were not pyrimidine photodimers, 6-4'-(pyrimidin-2'-one)-pyrimidines, base loss sites, or ring-opened purines. Therefore, purine-containing photoproducts, possibly dimers, were incised by the enzyme preparation.