To date, no report of three-dimensional ultrasonography in obstetrics has been available in the literature. In this study we describe the primary experience with three-dimensional ultrasonography for the prenatal evaluation of nine fetuses between 21 and 33 weeks of gestation. We found that it provides more information for clinical diagnosis than the traditional two-dimensional ultrasonography. The following advantages are notable: (1) the anatomic area of interest can be located first with the conventional real-time two-dimensional mode, then switched to reveal three-dimensional images, instantly; (2) three images are exhibited concurrently; (3) each of the three images can be arrayed separately and scrolled to search for the area of interest within the scanned volume; (4) the three-dimensional ultrasonography can be equipped with Doppler color flow mapping for the study of the fetal cardiovascular system. In conclusion, we believe that three-dimensional ultrasonography can greatly strengthen diagnostic potential, which deserves obstetricians' attention.