Clinically nonfunctioning pituitary adenomas are the most common types among pituitary adenomas. These tumors are usually diagnosed in their later stages due to the absence of clinical symptoms and detectable hormonal hypersecretion. Although these tumors are benign, they are hard to be completely removed during neurosurgery due to the massive invasion into the surrounding tissues at diagnosis. Furthermore, relapse is common. In recent years, medical treatment of pituitary adenomas has witnessed a rapid development. New medications have shown certain effectiveness in reducing the tumor size and improving the clinical symptoms.