Micropenis refers to an extremely small penis with a stretched penile length of less than 2.5 SD below the mean for age or stage of sexual development. It should be differentiated from a buried or hidden penis and aphallia. It is important to use a standard technique of stretched penile measurement and nomograms for age to identify children with micropenis. All children above 1 year of age with a stretched penile length of less than 1.9 cm need evaluation. Based on etiology they can be classified as hypogonadotropic hypogonadism (hypothalamic or pituitary failure), hypergonadotropic hypogonadism (testicular failure), partial androgen insensitivity syndrome and idiopathic groups. The help of a pediatric endocrinologist, geneticist, pediatric surgeon and/or urologist is often necessary. Growth velocity is an important determinant of associated hypothalamic or pituitary pathology. GnRH and/or hCG stimulation tests are often helpful in evaluating the etiology. Similarly chromosomal studies are indicated in a few. Often the diagnosis is inferred by the presence of clinical features suggestive of a syndrome usually associated with hypogonadotropic hypogonadism. Irrespective of the underlying cause a short course of testosterone should be tried in patients with micropenis and an assessment of the penis to respond should be made. Transdermal DHT has also been reported to be effective in prepubertal children. Children with hypopituitarism and GH deficiency respond to appropriate hormonal therapy. Surgical correction is not indicated in the common endocrine types of micropenis. Many studies have shown that most testosterone treated children have satisfactory gain in length of penis and sexual function. Thus sexual reassignment is done very infrequently now.