Results are given on tolerability and bioavailability of an intramuscular immunoglobulin (Ig) preparation (BI 2.011) with high titer against cytomegalo-virus (CMV). For rapid and long-lasting protection a dosage of 0.2 ml/kg body weight anti-CMV-Ig with a titer of 1:50 000 (Enzyme-Linked Immunosorbent Assay) is recommended. Prophylaxis should be taken into account in seronegative patients suffering from immune defects, that experience transplantation surgery and/or multiple injections of blood products.