317 hospitalized children and 86 healthy children were collected between April 4, 1991 and April 3, 1992 were detected for IgM antibodies to Legionella using ELISA with sonicated and EDTA antigens of 9 species (15 serogroups). The total positive rate was 13.25% (42/317) in hospitalized children and 2.33% (2/86) in healthy children. Legionellosis was diagnosed in 35 cases, of which 25 (11.68%) with respiratory illnesses, 5 (5/15) with kidney diseases or blood diseases and 1 (1.45%) with other disease. The proportion of legionellosis was 11.04% (35/317). Of the 15 antigens tested, significant antibodies levels were detected in 11. Tatlock micdadei constituted 47.62% (20/42). Lp(1-6)23.81% (10/42) and L. bozemane 14.29% (6/42). There was higher proportion of legionellosis in elder children and in summer time.