The purpose of this study was to survey the trends of supply, and geographic and age distribution of obstetrician-gynecologists and pediatricians in Japan with contrast to the decease in the number of children from 1980 to 1996. The data obtained from the survey of physicians in Japan were statistically examined using the Lorenz curve and the associated Gini index. The obstetrician-to-newborn ratios (ObsNRs), which were calculated from the data of the duplicated registration, decreased from 1980 to 1984 in 12 prefectures. The ObsNRs increased from 1984 to 1990 in all 47 prefectures. The ObsNRs slightly decreased from 1990 to 1996 in 31 prefectures. The pediatriciantochildren ratios (PedCRs) had increased from 1980 to 1996 in 45 of 47 prefectures. Both ObsNRs and PedCRs differed by more than twice between the lowest and the highest prefectures. The Lorenz curves and Gini indices for the distribution of both obstetrician-gynecologists and pediatricians showed no remarkable change during this period . The proportions of young doctors aged 39 years or younger were significantly lower in obstetriciangynecologistsand pediatricians than in the whole physicians in Japan. The present conditions of supply and geographic distribution of the obstetrician-gynecologists and pediatricians in Japan were considered to include several problems. Especially, considering the decreasing of the ObsNRs in many prefectures and the age distribution of obstetriciangynecologists and pediatricians, a special emphasis on the supply of young obstetriciangynecologists and young pediatrician should be put in medical policies of Japan.