Given in subtoxic doses to the rat, ergotamine produced tail gangrene in not more than 20% of animals. The incidence rate of ergotamine gangrene was not influenced by acute Mammation (carrageenin, dextran oedema). However, when inflammation was produced by immersing the tail of the rat in dimethyl sulfoxide, the incidence rate of ergotamine gangrene was greatly increased. The gangrene-inducing effect of ergotamine was significantly increased in rats with adjuvant arthritis or 6-sulphanylamido-indazole arthritis. Like arthritic rats, rats with lathyrism due to chronic treatment with aminoacetonitrile were also more sensitive to the gangrene-inducing effect of ergotamine. Ergotamine-induced tail gangrene in adjuvant arthritic rats is a good model for use in research for drugs which are effective against the vascular complications of ‘collagen’ diseases.