The effects of adrenalectomy on hair-loss have been studied in this laboratory for a period of 2 years, using rats. Experiments reported below are representative of the results now to hand. Methods White and black rats, raised in this laboratory, were used for the experiments. Adult animals, weighing c. 200 g. proved suitable. The hair-loss of young rats was small. Extirpation of the adrenals was effected under ether narcosis by dorsal approach. In sham-adrenalectomy, only one adrenal was actually removed whereas the second gland was merely exposed. In these cases the wounds caused by operation healed much more rapidly than in complete adrenalectomy. In many experiments the rats were rubbed down with a mixture of petroleum and linseed oil (1: 5) 3 or 4 days before the operation and afterwards maintained in specially disinfected and isolated cages. Moulted hairs were caught on a fine wire mesh, placed under the cages,