Histological aspects and changes in wet weight were studied on rat soleus muscles after dennervation by cutting the sciatic nerve. The muscles were removed after a variable period of time from the third to the fiftieth day. There was a progressive fall off in wet weight and after the third week the muscles underwent 50% atrophy. Histological changes were most striking on sarcolemmal nuclei; they became vesicular, enlarged with prominent nucleolus and there was an apparent increase in their number. The muscle fibres changed their shape, becoming rounded and there was a 50% reduction in muscle fibre diameter after 50 days. Connective tissue abnormalities were minimal after 50 days and the striations remained intact.