Indirect immunofluorescence and enzyme-linked immunosorbent assay to detect serum antibodies against Legionella pneumophila serotype 1 were compared. A very good agreement was found with the great majority of serum samples (85.07%). For detecting high antibody levels and rise in antibody titres, both methods seem to be suitable, however for the detection of relatively low antibody titres, very important in epidemiological studies, enzyme immunoassay could be more accurate.