CCL18 is increased in the serum of MF patients. The concentration of CCL18 in serum samples of 6 healthy controls, 8 atopic dermatitis (AD) patients, and 10 MF patients (5 in MF patch or plaque stage and 5 in MF tumor stage) were determined by ELISA. In MF patients, CCL18 concentrations (mean ± SD, 59 ± 17 ng/mL) were significantly three times higher compared with their healthy counterparts (18 ± 4.4 ng/mL; ***P = 0.00005). The differences between patients in MF patch or plaque stage (51 ± 9.2 ng/mL) and MF tumor stage (68 ± 19 ng/mL) were not significant. For positive control, AD patients were tested and had significantly higher levels (78 ± 30 ng/mL, **P = 0.001) compared with healthy controls. Values were not significantly different than those of MF patients.