In Korea, tsutsugamushi disease is a recently recognized infection. It has become clear that it is more prevalent than leptospirosis or hemorrhagic fever with renal syndrome. Accurate diagnosis of the disease is necessary for the selection of effective antimicrobial agents which can prevent fatalities and shorten the course. For the diagnosis, various serologic tests are used. Sensitivity and specificity of a test depend on various factors. In this report, microbiological aspects of the infection were briefly described and the Weil-Felix, indirect immunofluorescence and indirect immunoperoxidase tests were compared for their applicability in routine use and usefulness in the diagnosis. Their interpretations were also briefly discussed.