We present a case of retroperitoneal teratoma in a 4-year-old girl in which a Wilms' tumor-like element was predominant, unlike the usual pattern of the immature or malignant teratoma. Mature elements were composed of adipose tissue, neural plexus and ganglia, cartilage, smooth and skeletal muscles, and glandular epithelium of the respiratory and gastrointestinal types. Three months after complete excision of the mass, a recurrent tumor developed. It consisted of only nephroblastomatous elements without teratomatous components. Theories for the histogenesis of this rare tumor are discussed.