The gynecological diseases encountered in children are vastly different from those that commonly affect adults, and some affect only specific age groups of children. Therefore, knowledge of the age-related developmental changes and common abnormalities that occur in the uterus and ovaries from the newborn period to adolescence is necessary to evaluate the pediatric female pelvis. US is the primary screening modality and is often the only tool necessary for the diagnosis of disorders related to nonneoplastic ovarian cysts, ambiguous genitalia, precocious puberty, and pelvic mass or pain. CT and MRI are generally second-line modalities and have important roles, especially in the global assessment in a neoplasm or an inflammatory process that extends beyond the scope of US. MRI is also useful for evaluating complex urogenital anomalies. This chapter reviews gynecologic diseases commonly encountered in children as well as developmental changes of the genital tracts. Congenital anomalies, functional ovarian cysts, ovarian torsion, and tumors are covered in more detail in other chapters.