Whole-cell immunofluorescent antibody (IFA) tests for detection of anti-Bartonella henselae immunoglobulin (Ig) G are commonly used to diagnose cat-scratch disease (CSD). The need to cultivate B. henselae in Vero cells for antigen preparation and the absence of routinely applied IFA assays for IgM constitute the major disadvantages of this form of test. We describe the results of an enzyme immunoassay (EIA) for IgM and IgG that used N-lauroyl-sarcosine-insoluble outer membrane antigens from agar-grown B. henselae performed in 84 patients with definite CSD (regional lymphadenitis, cat contact, and > or =1 confirmatory test: polymerase chain reaction, skin test, or B. henselae culture). Although this method has been used as a diagnostic tool in several case reports, it has not previously been evaluated in a large study of definitively proven CSD cases. Results of this study indicate that the EIA described herein can play an important role in the serodiagnosis of CSD, although improvement of the sensitivity, particularly that of the IgM, would be desirable.