The menstrual cycle is nature's repeating preparation for pregnancy. Each month, the uterine lining develops in anticipation of implantation by a fertilized ovum. If this occurs, hormones from the reproductive organs stabilize the vascular tissue of the endometrium which provides an environment for the developing embryo. If the awaited implantation does not occur, the endometrium is sloughed due to a rapid drop in circulating levels of progesterone. This process starts during the early teenage years of a female's development (menarche) and repeats 400-500 times over the next 40 years. Normally, this process is interrupted only by pregnancy; however, other factors can certainly influence both the cycle length, volume, and the duration of each menses. Ultrasound imaging provides a noninvasive method to visualize the internal reproductive organs, the endometrium, and the embryo if implantation occurs. This relatively inexpensive evaluation provides an easy and cost effective method to examine potential problems associated with the female reproductive organs. Advances in computer software and hardware coupled with new ultrasound equipment has provided exciting 3-D and 4-D images that generate near life-like images. In the guiding hand of a trained physician or sonographer, ultrasound enhances diagnostic capability and gives reassurance to the patient.