The transplantable MC‐29 virus‐derived hepatoma is a suitable model for studying the influence of immune status on virus‐derived hepatomas in chickens. It was found that both humoral and cellular immunologic reactions have a role in the pathogenesis of virus‐derived hepatomas and that virus‐derived hepatomas con be influenced by nonspecific Immunostimulation. The lymphoid system was profoundly altered in hepatoma‐bearing chickens; this cannot be neglected when studying correlations between immune reactions and carcinogenesis. Profound changes were also observed in protein synthesis and the steroid receptor system of hepatoma‐bearing chickens compared to healthy birds; this also complicates the understanding of the role of immune mechanisms in carcinogenesis.