Summary. Epstein–Barr virus (EBV)‐associated B‐cell lymphoproliferations may arise in solid organ transplant recipients. In these patients, an insufficient control of EBV‐infected B cells commonly occurs. Antiviral treatment against EBV may represent a causal, relatively low‐toxic treatment option. Treatment with foscarnet, an inhibitor of viral‐DNA polymerase, in three patients with EBV‐associated post‐transplant lymphoproliferative disease (PTLD) after heart (n = 2) and heart/kidney transplantation (n = 1), who did not respond to, or were not eligible for reduction of immunosuppression, resulted in complete remission (48+, 27 and 15 months respectively). Response of PTLD to antiviral treatment correlated with the expression of lytic phase antigen BZLF1/ZEBRA protein, an early antigen of lytic EBV‐activity, in the biopsied PTLD specimens.