In order to study the adverse effects of manganese on neuro-endocrine and cardiovascular system, radioimmunoassay (RIA) was used to test the blood prolactin concentration and plasma renin activity among manganese-exposed workers. The result showed that the blood prolactin concentration and Plasma renin activity in manganese exposed workers were significantly higher than those of control group. It suggested that manganese exposure might affect the function at tubero-infundibular area and renin-angiotensin aldosterone system.