A total of 37 out of 13,234 pools were retested (23 positive pools and 14 pools falling into the area between the cut-off point and the cut-off point minus 10%). Retesting yielded 5 negative pools, 26 positive pools and 6 pools being within the 'cut-off - cut-off minus 10%' area. Thus the latter 32 pools (n=160 sera) were retested on an individual sera-basis yielding 38 positive sera and one 'cut-off -cut-off minus 10%' sera. The western blot gave 5 positive samples, which corresponded to a prevalence of 1/13,000 (0.01%), in accordance with prevalence estimates from earlier serosurveys and the national HIV registry.