【Background】Today most patients with congenital heart disease (CHD) can survive into adulthood. Reports regarding the number of adults with CHD in Japan are scarce. Our study aims to define the number of adults with CHD. 【Material and Methods】The expected numbers of infants with major CHDs since 1947 were calculated from birth and mortality rates. We estimated the numbers of CHD survivors from data on unoperated histories and long-term survival rates. The number of death from 1968 to 1997 was analyzed using individual death certificates held by Japanese government. 【Results】In 1967, 149,267 patients with CHD including 48,918 adults were assumed to be alive. From 1968 to 1997, 548,360 patients with CHD were born and 82,919 died. Total 608,648 patients, including 300,165 children (49%) and 308,483 adults (51%), were estimated to be alive in 1997. In 2007, 401,245 adults are estimated to be alive. From 1997 to 2007, about 9,200 adults have been increasing every year. 【Conclusions】The prevalence in adults with CHD in Japan has been explosively increasing from 1967 to 2007. Total 401,245 adults with CHD are alive in 2007 with annual increase of 9,200. These data are useful for further establishment of the special facilities and resources caring for adult CHD patients in Japan.