We report here a case of an HIV-uninfected, anti-hepatitis C virus (HCV) positive haemophiliac, who was transfused with blood and intermediate purity factor VIII concentrates. Since 1988, a progressive decline in the CD4+ T-cell count was recorded, and in 1993 a B-cell non-Hodgkin's lymphoma (B-NHL) was diagnosed. The morphological appearance of the tumor with features of intermediate/mantle zone lymphoma, and the absence of EBV sequences within the tumor, ruled out the occurrence of a typical "opportunistic" lymphoma. However it is possible that the blood product therapy and its infectious complications may have played a role on immune function impairment.