Reference range for head circumference on the Tanner charts do not go beyond age 16. In this study the head circumference and heights of 354 adults in two British centres were measured. The centile charts constructed from these measurements show that adult head circumference is related to height. The mean head circumference of a male of average height is above the 97th centile for a 16 year old on the Tanner charts. The paediatric charts are therefore inappropriate for use in adult males.