DNA damage caused by reactive oxygen species is ubiquitous to all living organisms. More than 60 different base lesions have been identified, and the majority of these are removed via the base excision repair pathway. This pathway appears to represent a highly conserved and ancient mechanism of defence counteracting spontaneous DNA decay. In this review, we describe in more detail the Ogg1 enzyme and its conserved action of removing the oxidised base, 7,8-dihydro-8-oxoguanine (oxo(8)G). Recent updates include the cancer-prone ogg1/myh double knockout mouse and an elegant study which looks at the ability of hOgg1 to distinguish between the mutagenic lesion, oxo(8)G, and the vast majority of normal bases.