DNA sequences from simian virus 40 (SV40) have been detected in various human tumors, including non-Hodgkin's lymphomas (NHLs), by highly sensitive PCR techniques. However, there is a strong debate as to whether SV40 is present in lymphoma cells. Using immunohistochemistry and tissue microarrays, we investigated a series of French and Canadian cases of Hodgkin's lymphomas (HLs) and NHLs and tried to detect the SV40 large T antigen using routine paraffin sections with standard and highly sensitive catalyzed system amplification methods. None of the cases of HLs (n ‫؍‬ 250) or NHLs (n ‫؍‬ 232) were found to contain a single large T antigen-positive cell, whereas 2 positive controls were repeatedly stained. Therefore, our results do not support the hypothesis that SV40 is implicated in the etiology of human lymphomas.