HCV immunological assays have limited specificity due to considerable variability of genomic coding sequences. Accordingly, PCR RNA detection also shows variable incidence of HCV in a non-A, non-B (NANB) hepatitis context. We used in-house designed nested PCR applying primers from the 5' untranslated region in 150 thalassemic patients classified in four groups according to anti-HCV screening and glutamic-pyruvate transaminase (GPT) levels. Group A: anti-HCV+/high GPT levels; group B: anti-HCV+/normal GPT levels; group C: anti-HCV(-)+high GPT levels; group D: anti-HCV(-)+normal GPT levels. Viral incidence and concentration, both high in group A, decreased towards group D. Group C RNA incidence was unexpectedly high and, moreover, one control case proved HCV-RNA+. Compared with the Amplicor kit or primers were considerably more sensitive.