Diagnosis of scrub typhus is difficult because of its unspecific symptoms. The authors studied the correlation between serum adenosine deaminase (ADA) levels and scrub typhus, with the aim of aiding diagnose of the disease. The medical records of 64 children, who visited Wonkwang University Hospital from 2005 to 2015 for fever of undetermined origin, were analyzed retrospectively. Serum ADA levels were measured and indirect immunofluorescence antibody (IFA) assays were conducted. The patients were divided into two groups based on diagnosis of scrub typhus. Of 64 febrile patients, 39 were confirmed to have scrub typhus. Mean serum ADA level in the scrub typhus group (58.54±2.82 IU/L) was significantly higher than that in the non-scrub typhus group (29.30±4.03 IU/L, p<0.05). In the 25 non-scrub typhus patients, mean serum ADA level was significantly higher (50.24±8.52 IU/L) in patients with Mycoplasma infection than that in those with other diseases (19.46±1.39 IU/L, p<0.05). The study shows that in patients with only fever who are difficult to diagnose, serum ADA levels substantially aid the diagnosis of scrub typhus. Ed:- please consider carefully