A sandwich enzyme immunoassay by a one step procedure for total IgE in human serum is described. This method is a modification of a two steps sandwich procedure which uses glutaraldehyde-treated tubes and antibody conjugated with peroxidase. The procedure described is characterized by immune reactions performed in one step for one hour and by a substrate solution containing orthophenylene diamine. The standard-curve is linear between 0 and 12 Ul/tube. The coefficient of within-assay ranges from 11,3 to 5% according to the concentrations. The coefficient of between-assay is 7,7% for IgE concentration of 233 kUl/l. In 107 serums, the regression equation and coefficient of correlation to another enzyme immunoassay (Phadezym IgE Prist) are: y = 0,89 X + 6,72; r = 0,98.