Young, growing female Sapphire mink presenting a high incidence of infectious plasma-cytosis were injected with Escherichia coli endotoxin for a period of approximately 4 months. The injections consisted of 1 mg each and the animals received a total of 29 inoculations. After 3 months of experimentation, there was no significant difference between the weights of the test animals and the control animals. A slight positive effect of endotoxin treatment was observed towards the end of the experiment when the mink were exposed to poorer nutritional conditions and received frozen feed and drinking water. Approximately 60 per cent of the experimental animals developed amyloidosis. These observations suggest that the endotoxin injected was not “toxic” in any respect other than its amyloidogenic action.