The onset of puberty may be late - in the latter part of the predicted normal range or truly delayed - beyond this range. The latest age to start is usually regarded as 13 years in girls and 14 years in boys. There may also be a delayed completion of puberty, 16 years in girls and 17 years in boys. The initial approach requires a detailed history and clinical examination to exclude other medical or psychological problems. The presence or absence or pubertal signs should be documented. Investigations should be targeted at ruling out any medical causes and determining whether the delay is due to central gonadotropin deficiency (hypogonadotropic hypogonadism) or a gonadal disorder (hypergonadotropic hypogonadism). Physiological or constitutional delay of growth and puberty (CDGP) is more common in boys but is a diagnosis of exclusion. Current research suggests that CDGP and congenital hypogonadotropic hypogonadism have distinct genetic profiles which may aid in the differential diagnosis. Treatment may be given using low doses of sex steroids, testosterone or estradiol initially in a short course of 3-6 months but continuing in escalating doses mimicking the normal course of puberty, watching regularly for the spontaneous resumption of progress and gonadotropin secretion. In gonadotropin deficiency, sex hormone treatment needs to be continued until completion of pubertal development and growth. Counselling, reassurance and support are key elements in the management of adolescents with delayed puberty.