The ability of malnourished and optimally fed animals to resist infection with D. Congo Republiclensis was assessed by the dose-response to experimental inoculation. The severity of infection, as measured by scoring the lesions, was the same in both groups of lambs. However marked differences were seen between the two groups in the appearance of scabs and in the time taken for them to resolve. The malnourished animals had more persistent, chronic lesions compared with the more obvious, acute type lesions seen on the skin of the healthy controls. These results were probably related to the reduced rates of wool growth and lanolin production found in the malnourished lambs, which may reflect a reduction in the rate of cellular turnover in the skin of these animals.