BACKGROUND: Atopic dermatitis is a chronic inflammatory relapsing skin disorder. It has been shown that urinary LTE4 and serum ECP level are elevated and correlated with disease activity. OBJECTIVE: We performed this study to measure the urinary LTE4 and serum ECP level in atopic dermatitis, and to evaluate the correlation between their levels and the clinical severity of atopic dermatitis by using SCORAD index. METHOD: We recruited 65 children with atopic dermatitis and 15 children with healthy control. We classified the atopic dermatitis patients by using SCORAD and excluded any other allergic or infectious diseases. In all children, serum ECP and urine LTE4 were measured. RESULT: Serum ECP levels were not significantly different between atopic dermatitis (39.1+/-34.9microgram/L) and healthy children (13.1+/-7.7microgram/L), and were not significantly correlated with SCORAD index in atopic dermatitis children. (R2=0.097, P<0.05) Atopic dermatitis children (212.3+/-135.6 mmol/mol creatinine) had significantly higher urine LTE4 levels than healthy controls (57.9+/-31.94 mmol/mol creatinine). Urine LTE4 levels were significantly correlated with SCORAD index (R2=0.664, P<0.05). CONCLUSION: Urine LTE4 level was significantly correlated with SCORAD index in children with atopic dermatitis and may be a useful marker for disease activity in atopic dermatitis.