The purpose of this study was to retrospectively investigate the relationship between age and clinical manifestations and laboratory findings in patients with measles. The study included 216 patients admitted to a hospital in Daejeon, 1 of the largest cities in South Korea, during the 2000-2001 measles outbreak: very young children (<2 y old; 159 patients), school age children (9-11 y old; 34 patients), and young adults (>16 y old; 23 patients). Few of the very young children (9%), but most of the older children (86%) had a history of a prior measles-mumps-rubella vaccination. There were no statistical differences between the 3 groups in terms of the total duration of fever, length of hospitalization, occurrence of complications (defined as hospitalization for more than 7 d) or anti-measles IgM positivity. A reduction in the number of white blood cells and lymphocytes was observed in all age groups. The levels of C-reactive protein were not different between very young children and older children, but hepatic involvement was more prevalent in young adults. In conclusion, the clinical course including the complications experienced was similar in all the measles patients regardless of age.