Serum soluble interleukin 2 receptor (IL-2 R) was determined by the ELISA method in 29 cases of IgA nephropathy and 50 healthy controls. The results showed that the value in IgA nephropathy cases was significantly higher than that in healthy controls. Furthermore, among the cases of IgA nephropathy, the value was significantly higher in the groups with hypertension, elevated serum IgA and depressed creatinine clearance than in that of the corresponding controls. These findings suggest that serum soluble IL-2 R can serve as a prognostic index of IgA nephropathy.