Objective To study the change and the clinical significance of neopterin in patients with rheumatic fever. Methods The concentrations of serum neopterin in patients with acute rheumatic fever(ARF), chronic inactive rheumatic heart disease(CRHD) and healthy controls were measured by ELISA method. Results The concentrations of serum neopterin in patients with ARF(7.84±6.31 nmol/L) were significantly higher than those in patients with CRHD (4.31±2.59 nmol/L, P<0.05) and healthy controls (2.91±2.26 nmol/L,P<0.01); the concentrations of serum neopterin in patients with CRHD were almost the same with those in the healthy controls (P>0.05). Conclusions The concentrations of serum neopterin increased in ARF, while decreased in CRHD. The serum neopterin levels can reflect the activity of the disease. Neopterin may be used as a marker to detect T cells activated by ARF.