Hodgkin's-like lymphoma involving the lung, mediastinum, liver, kidneys and mesenteric lymph nodes was diagnosed in a ferret. The diagnosis was based on the presence of an admixture of CD3+ small lymphocytes with smaller numbers of macrophages, eosinophils, and large, pleomorphic, frequently multinucleated, Reed-Sternberg-like cells which were immunoreactive to BLA.36 monoclonal antibody. In addition, the liver, pancreas, small intestine and lungs were infiltrated with moderate to large numbers of eosinophils, forming eosinophilic granulomas with occasional deposition of Splendore-Hoeppli material, supporting a diagnosis of hypereosinophilic syndrome. The concurrent diagnosis of hypereosinophilic syndrome and Hodgkin's-like lymphoma in this ferret provides further support to the concept that, in animals, multisystemic eosinophilic infiltrates may be caused by the abnormal proliferation of T lymphocytes, as has been demonstrated in man.