The Blood Transfusion Service introduced screening for Hepatitis C antibody (HCV) in September 1991. This is done by second generation enzyme linked immunosorbent assay (ELISA) tests. We present a case of post-transfusion hepatitis C hepatitis in a patient with myeloma. Infection was acquired before screening was introduced. Both the patient and the infected blood donor were diagnosed using ELISA assays and the polymerase chain reaction (PCR). In this way we prevented the blood donor from spreading the virus via subsequent blood donations. There were some interesting discrepancies in the HCV assays. Blood samples, when tested by different methods, gave both positive and negative results. The results also varied according to when the blood samples to be tested were taken. The case illustrates the importance of confirming positive results and that no single laboratory test is entirely satisfactory in diagnosing HCV infection.