Placental site trophoblastic tumor is a rare trophoblastic neoplasm with the potential for metastatic disease and death. Difficulty diagnosing these tumors and predicting their biologic behavior has clouded attempts to successfully outline individual treatment plans. This review details current knowledge of the origin and clinical behavior of this rare form of trophoblastic disease. The use of various markers to predict clinically aggressive behavior is reviewed critically, and treatment is recommended on the basis of recently published clinical series.