At the height of the United Kingdom influenza A epidemic in December 1989, three children receiving treatment for non-T cell acute leukaemia developed pancytopenia with concomitant influenza A infection. Bone marrow histology showed prominent marrow erythrophagocytosis by morphologically mature histiocytes, consistent with the picture of virus associated haemophagocytic syndrome (VAHS). In two cases there was an initial spontaneous recovery, though recurrence of VAHS developed in one case in association with a different viral infection (cytomegalovirus) following autologous bone marrow transplantation. The third child died from cardiorespiratory failure secondary to infection with influenza A and Klebsiella pneumoniae sepsis. It is suggested that influenza A should be added to the list of infective causative agents.