In 1995, AAFACT, a new monoclonal purified factor VIII concentrate (FVIII), derived from human plasma, was introduced in the Netherlands. The monoclonal purification based production process includes a viral inactivation step by solvent/detergent treatment. Products manufactured according to this procedure, for example Hemofil M are used worldwide. The aim of the present study was to assess inhibitor development in a large cohort of previously treated patients (PTPs) who were followed up for 10 years. In addition, efficacy, HIV and hepatitis C virus (HCV) transmission, and allergic reactions were monitored. All 165 patients with severe haemophilia A (FVIII<1%) known at the van Creveldkliniek who ever used AAFACT during the period from October 1995 to September 2005 were included. Two of them were previously untreated patients (PUPs) and two others had <50 exposure days. Data on FVIII consumption, number of exposures, bleedings and hospitalization days were collected from start of AAFACT until last clinical and laboratory evaluation while on this product. At the end of follow-up, 91 patients were still using this plasma-derived FVIII. Median age at start of follow-up was 26 years (range 1-52). None of the patients reported lack of efficacy. Median FVIII consumption per patient during follow-up was 2058 IU kg(-1) bodyweight per year, and median number of exposures was 148 per year. During 1029 patient-years of follow-up, one inhibitor was diagnosed in a previously treated patient PTP. This patient developed high titre inhibitor following surgery for which he, during 1 week, had been treated with continuous infusion with recombinant FVIII. No inhibitor occurred during 68 cases of surgery using continuous infusion with AAFACT. No viral transmissions or other adverse events occurred during 10 years of follow-up; AAFACT appeared to be an effective and safe FVIII product.