We performed clinical and virological studies on 79 children with hand, foot and mouth disease (HFMD) who had been admitted or visited to the department of Pediatrics, Asan Medical Center from February to August, 1990. The results were as follows; 1) There were total of 79 cases with hand, foot and mouth disease during this period. The aseptic meningitis was combined in 18 cases (22.8%). 2) The male-to-female ratio of HFMD was 2.03 to 1, but that of aseptic meningitis was 8 to 1. 3) Hand, foot and mouth disease occurred more frequently in under the age of 5 years, and the aseptic meningitis in under the age of 1 year. 4) Hand, foot and mouth disease and the aseptic meningitis occurred mostly in May and June. 5) In addition to the skin manifestations characteristic in hand, foot and mouth disease, some of the patients with aseptic meningitis had the following symptoms: change of consiousness, seizure, monoparesis in the upper extremity, paraparesis in the lower extremity. 6) The causative agent of hand, foot and mouth disease associated with the aseptic meningitis in Seoul in 1990 seemed to be enterovirus 71 according to the serologic study.