Three-dimensional ultrasound (3D US) is a modality of choice for prenatal diagnosis of congenital malformations. But 3D-four-dimensional US(4D US) is of utmost importance also to achieve pregnancy. 3D US plays an important role for diagnosis of PCO, to assess ovarian reserve and response and thus to decide optimum stimulation protocols. It adds to the information on follicular maturity and endometrial receptivity, thus improving the chances to achieve pregnancy for patients under treatment for fertility. 3D hystero-contrast-salpingography (HyCoSy) has also proved itself to be one of the best modalities for assessment of tubal patency. In this article, the role of 3D and 4D US is discussed for the following. I. Pretreatment assessment of the females desiring fertility which includes assessment of uterus and fallopian tubes. II. Monitoring of infertile females undergoing treatment. III. Assessment of very early pregnancy - especially in abnormal locations.