Important factors to assure the safety of plasma-derived products manufactured on an industrial scale are initial screening of the source material and validation of the manufacturing process in accordance with issued EEC guidelines and US ‘Points to Consider’. Pharmacia's manufacturing process for immunoglobulins contains a specific virucidal step, in which lipid-enveloped viruses are effectively inactivated with a solvent/detergent (SD) combination consisting of 0.3% tri(n-butyl)phosphate and 1% Tween 80. Results from virus validation studies of scaled-down versions of Pharmacia's manufacturing process for immunoglobulins demonstrated extensive removal of relevant and model viruses. More than 5.0 logs of human immunodeficiency virus type 1 (HIV-1) were inactivated in the SD step and, in total, more than 31 logs of HIV-1 were eliminated in the steps studied. Comparison between SD treatment and heating at 60°C of lipid-enveloped viruses in different protein solutions demonstrated that SD treatment is the superior procedure. Polio virus is a model often used in virus validation studies to predict effects on non-enveloped viruses. Because polio virus is more sensitive to heat than are hepatitis A virus (HAV) and human parvovirus B19, thermal inactivation studies with polio virus may result in an overestimation of the effects on HAV and B19.