An isolate of Fusarium oxysporum from corn associated with Kaschin-Beck disease in humans was tested for its ability to induce tibial dyschondroplasia (TD) and toxicity in chicks. Both leghorn and broiler chicks were fed diets in which corn was replaced with varied amounts (0% to 50%) of the F. oxysporum culture grown on sterile corn, or with known TD-inducing agents. F. oxysporum did not affect body weight in either type of chicks. In leghorn chicks, neither F. oxysporum nor the known TD-inducing agents (F. equiseti, 4%; tetramethylthiuram disulfide [Thiram], 35 ppm) caused TD. However, F. oxysporum at high levels (50%) and the two known TD-inducing agents reduced interdigital cutaneous response to phytohemagglutinin-P challenge. In addition, Thiram also reduced body-weight gain by more than 17%. In female broiler chicks (Cornish Rock), F. oxysporum not only decreased cell-mediated cutaneous response to phytohemagglutinin-P but also increased TD incidence; these same effects were observed with F. equiseti and Thiram. Histological examinations revealed similar pathological changes among dyschondroplastic lesions induced by F. oxysporum, F. equiseti, and Thiram. Results of this experiment indicate that the isolate of F. oxysporum from the region in which Kaschin-Beck disease is endemic can induce TD in broiler chicks and that it is immunosuppressive.