Summary:Treatment with human recombinant interleukin‐2 (rIL‐2) is associated with multiple organ dysfunctions, including hepatic and cardiac toxicities. We present a rabbit model that may be highly suited to investigations of these organ toxicities. Rabbits were treated with rIL‐2 at a dose of 3 × 106Cetus units/kg/day in divided doses every 8 h for 9‐11 doses. Control animals received either excipient or 5% dextrose in water. Treatment with rIL‐2 resulted in hepatic and myocardial infiltration by lymphocytes and mononuclear cells. Monoclonal antibody‐staining techniques revealed a high percentage of T lymphocytes. It remains to be shown whether these infiltrates are responsible for the respective organ toxicities or represent merely an epiphenomenon of rIL‐2 treatment.