N-Methylpurine-DNA glycosylase (MPG) removes N-methylpurine and other damaged purines in DNA. RT-PCR analysis revealed MPG mRNA expression at various tissues of fetal development from day 8 to day 18 fetus and day 400 mature adult. The MPG transcripts were abundant during fetal development in mice. In placenta, the MPG mRNA was continuously decreased from day 8 post coitum (p.c) to day 18 p.c. fetus. The high level of mRNA in fetal brain and liver was drastically declined in day 400 mature adult. The expression of MPG, originally characterized by its highest level of expression in the epididymis of adult mouse, was detected with high level in several other reproductive organ, including the ovary, oviduct, testis, vas deference, uterus, and seminal vesicles. These results demonstrate developmental stage- and tissue-specific variation of MPG gene expression.