In spite of donor selection, screening of donated blood for anti-HIV-1, anti-HIV-2, anti-HCV and HBsAg, inactivation and elimination processes, there is still a residual risk of haematogenically transmissible viruses in plasma pools and products. As an additional measure to reduce risk of viral contamination, screening of individual donated units and minipools on HCV RNA has become mandatory in Germany. In the present study, 142 HBsAg-, anti-HCV- and anti-HIV-1/-2-negative plasma pools and derived products (immunoglobulin preparation and factor IX preparation) were tested by PCR for the presence of HAV, HBV, HCV, GB virus C (GBVC) and HIV-1 nucleic acids. All pools and plasma preparations were derived from blood donated between 1994 and 1996, before mandatory testing for HCV RNA was introduced. Twelve (8.5%) plasma pools tested positive for HCV RNA. A low copy number of HBV DNA was present in 9 (6.3%) plasma pools. HIV-1 RNA was not amplified from any plasma pool, whereas the prevalence of the GBVC RNA in pools was very high (82.4%). However, GBVC RNA could be detected in only 1 (6.3%) of 16 immunoglobulin (IgG) batches prepared from cryosupernatants yielding GBVC. HBV DNA and HCV RNA could not be amplified from 3 IgG batches originating from HBV or HCV nucleic acid-positive supernatants. Neither HBV nor HCV contamination was present in any of the 31 unselected immunoglobulin preparations. GBVC RNA could be detected in only 2 (6.5%) of the samples tested. Our results demonstrate the importance of HCV PCR testing of plasma pools since HCV RNA was detected in a relatively large proportion of the pools screened negative by conventional methods. The results underline the importance of the virus elimination methods integrated in the production process since no HBV or HCV nucleic acid could be detected in any batch of end product. Consequently, routine PCR testing of end products whose production involve virus elimination and virus inactivation methods is not to be recommended.