The use of pelvic ultrasound to investigate the subfertile female needs a close collaboration between the gynecologist and the radiologist. Ultrasonography is now a must in the investigation of ovulation disorders, along with clinical findings and hormonal assays. It allows estimation of the ovarian function, mainly estrogen secretion, through measurement of the endometrial thickness: endometrial atrophy or severe hypotrophy (thickness more than 5 mm) indicates hypoestrogenism. It also contributes greatly to the diagnosis of ovulation disorders, in particular polycystic ovary syndrome (PCOS) and primary ovarian failure (POF), along with the clinical/biological data. The ultrasound is sensitive in detecting those lesions that are responsible for infertility through interference with egg migration and implantation and/or with sperm progression, such as fibroids, polyps, synechiae, or malformations. The 3D ultrasound can help in the diagnosis of uterine malformations. The majority of tubal obstructions are secondary to sexually transmitted infections, particularly gonorrhea and chlamydia.