Sensitivity and specificity of the Directigen Flu A + B kit, a rapid test for influenza virus A and B, were evaluated. This test detects influenza A and B viruses separately by EIA. Reactivity of the kit was tested using a total of 23 isolates: 13 isolates of human influenza virus A (H1N1, H3N2) and 10 isolates of human influenza virus B. All of the isolates were tested positive and no difference in reactivity was found in antigenic variables and subtypes. The kit was only reactive to influenza virus A and B, not reactive to other viruses. Typical influenza A and B strains were tested for detection limit. 7.8 x 10(3) pfu/ml was a detection limit for influenza virus A (H1N1: Beijing/262/95), 4.7 x 10(4) pfu/ml for influenza virus A (H3N2: Kitakyusyu/159/93), and 3.1 x 10(4) pfu/ml for influenza virus B (Guangdong/05/94). The Directigen Flu A + B kit was a easy-to-use, rapid detection device and the kit has sensitivity and specificity equivalent to other diagnostic devices, suggesting the kit are useful in medical institutions.