Laboratory research that began in 1982 led to the licensing in the USA of a solvent/detergent (SD)-treated factor VIII concentrate in 1985. The licence was granted on the basis of several factors. First, studies had demonstrated the inactivation of several marker viruses (vesicular stomatitis virus, Sindbis virus, Sendai virus) and other viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), and non-A, non-B hepatitis virus (NANBHV; now known principally to be hepatitis C virus) added to the factor VIII concentrate just before treatment. Secondly, it had been realized that the relevant viruses in transfusion (e.g. HIV, HBV, NANBHV) all had lipid envelopes. Finally, laboratory, preclinical and clinical evidence indicated that factor VIII and other proteins present in the preparation were unaffected by SD treatment. The applicability of the SD method to a wide range of products and preparations, high process recoveries and a growing body of viral safety information linked with the failure of several other virus-inactivation methods to eliminate hepatitis transmission fostered the adoption of SD technology by more than 50 organizations worldwide. SD mixtures arc now used in the preparation of a diverse array of products. Numerous laboratory and clinical studies suggest that coagulation-factor concentrates and other SD-treated products prepared from plasma pools are now safer than the individual units from which they were derived. Also, a large body of evidence indicates that hepatitis A virus (HAV) is not typically transmitted by blood and blood products. Even if a rare unit contaminated with HAV was included in the plasma pool, protection is afforded by immune neutralization, other mechanisms of inactivation, and by removal. Where the possibility of HAV transmission has been reported, other factors may have contributed to its spread.