The subject matter in this volume was derived from papers presented at the Pediatric Andrology session of the 1st Pan American Congress of Andrology held in Caracas, Venezuela in February 1979, as well as from selected additional manuscripts of interest in this field. Prior to this session, identification of a distinct discipline and specialty devoted to pediatric andrology had not occurred, nor had it been conceptualized. Pediatric andrology encompasses many different areas: disorders of sexual development, structural disease of the genital organs, normal and abnormal puberty, undescended testes, genital tumors, gonadal function and its relationship to growth, virilization, fertility and gender identity all represent areas of specific interest, to name but a few. Andrology itself is a unique field, bringing together clinicians and basic scientists with diverse back- grounds. It should be noted that between one-half and three-quarters of the clinicians contributing to this issue conduct basic research as well. It has been this unique blend of basic research and clinical medicine which has done much to unravel many of these problems characteristic of this field.