Diagnosis of leprosy is usually made clinically and there are no tests available for the routine laboratory diagnosis of the disease. The aim of this study was to investigate the potential role of chemokines as biologic markers of disease activity. We used an enzyme-linked immunosorbent assay to measure chemokines in plasma of patients with leprosy (LE) and non-infected (NI) individuals. There were significantly greater concentrations of the chemokines CCL3 and CCL11 in plasma of LE patients than in NI individuals. When the use of CCL11 to differentiate LE patients versus NI individuals was evaluated, the area under the receiver-operator-characteristic curve was 0.95 +/- 0.03 (P < 0.0001). In a group of selected individuals, CCL11 was useful in diagnosis of leprosy, thereby suggesting that measurement of this chemokine may be useful as an aid in diagnosing leprosis.