In kidney transplantation, pretransplant serum sCD30 testing has been proposed in immunological risk estimation together with anti-HLA antibodies. We evaluated the risks associated with high pretransplant serum sCD30 in well HLA-matched cadaveric kidney recipients recruited in a clinical study comparing different immunosuppressive regimens. Rejection rate was similar in 37 recipients with high pretransplant serum sCD30 compared to 117 recipients with low serum sCD30 (16% vs. 15%, P=NS). Compared to pretransplant levels, the posttransplant sCD30 levels generally decreased, also in patients with rejection, although on day 21 posttransplant, rejecting patients had significantly higher relative sCD30 than nonrejecting patients (P<0.01). However, steroid-resistant rejection was associated with increasing posttransplant sCD30 levels. High pretransplant sCD30 values were associated with tubulointerstitial rejection. There was no correlation of sCD30 with delayed graft function. Good HLA matching seems to be effective in neutralizing the negative effect of a high pretransplant serum sCD30.