Leiomyosarcomas of the retroperitoneum are rare neoplasms, belonging to the soft-tissue sarcomas, a group that accounts for less than 1% of all malignancies. Signs and symptoms are nonspecific with abdominal pain being the most frequent complaint. Often the tumors reach a large size before being detected. Diagnosis requires examination of tissue obtained by biopsy. Due to the advanced nature of the lesion at the time of discovery, treatment is difficult and results are often unsatisfactory. Excision is the treatment of choice unless the patient has wide metastasis or is unable to tolerate surgery. Although radiation and adjuvant chemotherapy have been used in some cases, the prognosis for this lesion remains poor. This paper discusses the incidence, epidemiology, clinical presentation, diagnosis, pathology, and treatment of this rare malignancy.