Measles diagnosis has thus far been based on clinical symptoms in daily clinical practice. However, atypical cases are not uncommon; a simple and rapid method of measles diagnosis is clinically required. Lateral flow-based rapid diagnosis reagents are widely used for point-of-care testing in Japanese clinics, because it does not require special skills and facilities. We have developed a rapid diagnostic reagent for measles that employs the lateral flow method. The lower limit of detection of this reagent was almost the same for recombinant proteins of wild-type and vaccine strain, at 5.1 x 10(3) copies/test. This lower limit of detection and the specificity of this reagent suggest its efficacy for the diagnosis of measles infection.