Three-dimensional (3-D) ultrasound imaging is an emerging technology that has introduced a novel way to evaluate patient anatomy and pathology. Volume data are acquired by combining data from conventional two-dimensional (2-D) ultrasound images. The data generally are displayed with both multiplanar and volume-rendered images. Volume data can be rotated into a standard anatomic orientation and viewed systematically from any arbitrary orientation. This article reviews potential clinical applications of 3-D ultrasound in gynecology and obstetrics, and provides a rationale for the advantages of using 3-D ultrasound compared with 2-D ultrasound. In gynecology, reports suggest there are benefits related to evaluating congenital anomalies of the uterus and possible infertility, screening for endometrial cancer, diagnosis of fibroids and adnexal masses, and use of intrauterine devices (IUD) and 3-D sonohysterography. In obstetrics, the benefits involve evaluating the first-trimester gestational sac and embryo and identifying congenital anomalies of the face, skull, spine, heart, abdomen, and extremities.