International audience; The soluble form of CD30 (sCD30), a member of tumour necrosis factor receptor superfamily, has been used as a marker of disease activity in various lymphomas. Epstein-Barr virus (EBV) is a potent stimulator of CD30 expression. The study aims to evaluate whether sCD30 can be used as a diagnostic marker for EBV-associated infectious mononucleosis (IM) and post-transplant lymphoproliferative disease (PTLD). Plasma from EBV seropositive healthy controls (N=90), acute IM patients (n=90), non-PTLD heart/lung transplant recipients (N=30) and EBV-positive PTLD patients (N=23) was tested for sCD30 using a commercially available ELISA kit. EBV DNA was tested by real time quantitative polymerase chain reaction assay. Significantly higher sCD30 levels were observed in acute IM patients (median 242.9 ng/mL) compared to EBV seropositive controls (median 15.7 ng/mL; p