A mixture of Tri-n-butyl phosphate (TNBP) and Polysorbate 80 (Tween 80) is often used for virus inactivation during the manufacture of medicinal products derived from human plasma. This procedure, known as solvent/detergent treatment, is of high effectiveness for inactivation of enveloped viruses. Tween 80 can be manufactured from bovine tallow or from vegetable material. As the bovine-derived Tween 80 is normally used for the solvent/detergent treatment, the question has been raised whether vegetable-derived Tween 80 can be applied as an alternative substance for the solvent/detergent treatment. Comparable inactivation studies were therefore performed using Vesicular Stomatitis Virus (VSV), Pseudo-rabiesvirus (PRV), Semliki Forest Virus (SFV) and Bovine Diarrhoea Virus (BVDV). In principle, no differences were observed in the effectiveness of the solvent/detergent treatment when bovine or vegetable-derived Tween 80 was used. The comparability in the efficiency of both detergents for virus inactivation was shown to be independent of solvent/detergent concentration, of temperature (160 C and 6degreesC vs. 27degreesC and 25degreesC) and protein concentration (10% and 5% human albumin). In summary, vegetable-derived Tween 80 is of the same effectiveness as bovine-derived Tween 80, when used for virus inactivation by the solvent/detergent treatment. (C) 2002 The International Association for Biologicals. Published by Elsevier Science Ltd. All rights reserved.