The IgG and IgM titers to Bartonella henselae were determined by an enzyme immunoassay (EIA). The EIA test for detection of IgG and IgM antibodies to B. henselae concerning CSD showed that 8 (40%) of 20 patients with CSD had a serum IgG antibody titer of 12 EIA unit or more and that 5 (25%) patients had a serum IgM titer of 12 EIA unit or more. Totally 12 (60%) of the 20 patients with CSD were seropositive for B. henselae. The mean age of IgG positive patients were higher than IgM positive patients. The IgM antibodies to B. henselae disappeared within 4 to 12 weeks after onset of disease. The IgG antibodies to B. henselae disappeared within 3 to 8 weeks after onset of the symptoms in 2 cases of CSD. Another 2 cases CSD produced high levels of IgG antibodies in the acute phase of the disease. Different course of IgG and IgM antibody titers were found in sera from patients.