We assessed the sensitivity and specificity of the Capilia Flu AB rapid diagnosis kit for influenza that utilizes the immunochromatography method. Tested were 114 influenza like illness patients in the 2001/2002 influenza season. We used Capilia Flu AB and Infu A . B Quick, a rapid diagnosis kit based on enzyme immunoassay. As laboratory confirmation tests, influenza virus isolation and polymerase chain reaction (PCR) were done. Those patients with positive results from virus isolation or PCR were regarded as influenza patients. The sensitivities of nasal swab, pharyngeal swab, and nasal wash specimens were 82.8%, 80.0%, and 75.0%, respectively. The specificities of nasal swab, pharyngeal swab, and nasal wash specimens were 95.3%, 93.9%, and 100%, respectively. A total of 20 patients displayed different results in comparison of their nasal and pharyngeal swabs: 15 patients were positive with the nasal swab but negative with the pharyngeal swab and 5 patients were negative with the nasal swab but positive with the pharyngeal swab. Nasal swab would seem to be preferable in terms of sensitivity. The sensitivity and specificity of Capilia Flu AB were a little higher than those of Influ A . B Quick, but with no significant difference. The one-step operation of Capilia Flu AB is easier than the four steps required by Influ A . B Quick, but the time required to make a diagnosis is the same. No significant age related difference in the effectiveness of the kits was found. The Capilia Flu AB rapid diagnosis kit is useful in clinical practice because it has good sensitivity (about 80%) and specificity (about 90%), and it is easy to use.