A marked change in age distribution of measles inpatients from 1981 to 2002, namely the in-crease in number of infants under one year of age and that of young adult of 20-24 years were observed. Recent decrease in number of measles inpatients of 2-4 years of age seemed to result from the effect of vaccination against measles given to young children over 12 months of age. Relative increase of infant patients younger than 1 year of age appeared to result form the decrease in number of patients over 1 year old or from the absolute increase in number of infant patients below 1 year of age which arisen from decreased level of anti-measles antibody transferred from their mothers. To clarify which is the more important cause, however, further investigations will be necessary. Relative increase in adult inpatients of measles is speculated to result from the increase in number of adult susceptible to measles because they were not vaccinated against measles and did not contracted measles.