Cytomegalovirus (CMV) is a herpes virus with life-long persistence following primary infection. Forty percent of the population carry the virus by the age of 20 years and sixty percent by the age of 60 years. CMV infections are usually asymptomatic, but in the immuno-compro-mised patient reactivation or a primary infection may cause severe disease, with retinitis, colitis, hepatitis or pneumonia. TNF-α mediates host-resistance against micro-organisms and inhibits CMV replication and serum TNF-α is elevated during acute CMV-infections (1). TNF-α blocking agents (infliximab, etanercept and adalimumab) block the pivotal role of TNF-α in the inflammatory response. Efalizumab is a monoclonal antibody directed against the CD11a subunit of LFA 1 on lymphocytes, thereby blocking lymphocyte to antigen-presenting cells interaction and diapedesis. We describe here 2 cases of CMV infection in patients receiving biological treatment. CASE REPORTS