Daily injections of peanut oil for 17 or 18 days cause decrease in rate of growth of the rat, and testicular atrophy. Hence results in experiments in which peanut oil (and probably similar oils) are used as solvent vehicles for administration of material by injection may be misinterpreted. Oral administration of oestradiol (3 mgm. daily) to young mature rats for three weeks or more causes decrease in growth rate, relative decrease in size of kidneys, heart, spleen, muscle, and ovaries, little effect on the liver, marked decrease in size of testes, even to actual atrophy, and frequent enlargement of the adrenals in males, with occasional enlargement in females. The adrenals are discoloured to a maroon shade, whether enlarged or not, and evidence is advanced that they are undergoing a pathological change; any enlargement is not in the nature of hypertrophy. Oral administration of stilboestrol gives similar results. The general effects of oestrogens are more marked in male than in female animals. Loss of appetite and diminished food intake are among the general effects, but the mild chronic starvation so produced can only contribute in very minor degree to the other oestrogenic effects.In mild chronic starvation from food restriction the liver is invariably affected, while the adrenals are never enlarged nor discoloured.The effects of combined oestrogenic and thyroid administration seem to be neither additive nor truly antagonistic.