Epstein-Barr virus (EBV)-associated lymphoproliferative disorders frequently develop in patients with acquired immunodeficiency syndrome (AIDS). The lymphoproliferative disorders are usually treated with a combination of cytotoxic drugs, and virustatic medication is thought to be ineffective. However, we report about two AIDS patients with EBV-associated lymphoproliferative disorders not responding to a standard chemotherapy, who achieved complete tumour regression after virustatic therapy with foscarnet.