Disease of endocrine system includes ailments of endocrine organs and resulting of correlating target organs as hypertrophy、hyperplasia and atrophy. There are such many diseases that it is impossible to compile and instruct all these diseases, so this chapter mainly focus on frequent and common diseases. Of these disease, pituitary adenoma, diffuse nontoxic and toxic thyroid goiter, chronic thyroiditis, thyroid tumor, epinephrine tumor. diabetes mellitus, islet cell tumor and apudoma are instructed emphatically. Students are required to master concept of APUD system, new classification and its features of pituitary adenoma, characteristics of toxic and nontoxic thyroid goiter and chronic thyroditis, classification and their features of thyroid adenoma and carcinoma, and classification and pathogenesis of diabetes mellitus. In addition, there are questions attached in this chapter, which are required to finished after class, moreover, professional English vocabularies are also required to master.