The human OGG1 gene codes for a 38kD protein with an antimutator activity related to its capacity to excise the mutagenic base 8-OH-Guanine from DNA. Mutant forms of this gene have been found in lung and kidney tumors. The determination of the start of transcription allowed the definition of the promoter sequences for the gene. By transient transfection and a luciferase reporter assay a 135 base pair region immediately upstream of the transcription start is shown to have full promoter activity. Two CpG islands and an Alu repeat were identified within the promoter and the 5' sequences of the transcribed region. The lack of TATA or CAAT boxes suggests that OGG1 is a housekeeping gene. Consistently, its expression, measured as the transcription from the promoter or as the enzymatic activity in cultured fibroblast cell lines, does not vary during the cell cycle.