An epidemic of Echo 11 virus infection occurred in Gifu Prefecture in children. Epidemiological and virological investigations were performed. The results are as follows: 1) Echo 11 viruses were isolated from patients from January to September. Most viruses were isolated in July. 2) Echo 11 viruses were isolated from all areas in Gifu Prefecture, especially from Seino and Hida areas. 3) Cases isolated Echovirus 11 ranged from 0 to 10 years of age, and 83.7% of them were in the 0 to 6 year of age group. 4) Five types of viruses were isolated from 51 of 86 cases (59.3%), and the Echovirus 11 was recovered from 43 cases (84.3%). 5) Echo 11 viruses were isolated from patients of various clinical conditions, but most patients in which isolated Echo 11 virus was isolated had aseptic meningitis, 17 cases (39.5%). Aseptic meningitis occurred in a higher frequency in those above 3 years of age. 6) By the cross neutralizing test between the prototype, isolated strain in 1982 and isolated strains in 1993 of Echovirus 11, a remarkable antigenic variation was not found in isolates in 1982 and 1993.