The incidence of congenital uterine anomalies in the general population is between 0. 4% and 3. 2%. This chapter describes the principles of ultrasound diagnosis of uterine anomalies and compares the results with other available diagnostic modalities. The gold standard in the diagnosis of congenital uterine anomalies used to be a simultaneous laparotomy/ laparoscopy and hysteroscopy to visualize the serosal surface of the uterus and the endometrial cavity. The real breakthrough in ultrasound assessment of congenital uterine anomalies was the development of three-dimensional transvaginal probes. This technique involves the acquisition and storage of a volume of ultrasound information. Magnetic resonance imaging (MRI) has been shown to be effective for the diagnosis of congenital uterine anomalies with sensitivity and specificity up to 100%. The advent of three-dimensional ultrasound has greatly enhanced the ability to diagnose congenital uterine anomalies in an outpatient setting.