The chemical composition of the liver and skeletal muscle in rats which had been treated with 1·0 μg. oestradiol has been investigated. The water and electrolyte content, creatine and creatinine phosphorus fractions and total nucleoproteins were studied. The changes in the water content are reciprocal to those already described for the uterus. The creatine and creatinine content and the total nucleic acid do not change significantly. There is an increase of the acid-soluble phosphorus in the first phase of the water increase in skeletal muscle which is related to some of the changes of intracellular potassium. In the liver there is an increase of the total water content between 28 and 36 hr. after injection, which is also associated with changes of acid-soluble phosphorus and cell electrolytes.