Background: Pubertal status is an important determinant of many health-related behaviours and outcomes. It is therefore an exposure of interest for numerous outcomes, as well as being a confounder in many exposure. A non-invasive method of assessing maturation status based on the percentage of adult stature (predicted from parental height) that a child has attained has been developed. The percentage of predicted final height for an individual can be compared with age- and sex-specific references to give z-scores, which can then be used to assess the degree to which a child is advanced or delayed in maturation status. The aim of this project is to apply this method to data from participants of the Avon Longitudinal Study of Parents and Children (ALSPAC). Comparison of these measures with other puberty assessments: age of menarche for girls, and for boys and girls, assessments of puberty based on questionnaires in which the child's parent or guardian was asked to identify which line-drawing most closely resembled the child. This method describes 'Tanner'stages ranging between I and V, with I being least sexually mature. Since heights at age 18 are also now available for the ALSPAC cohort, we can compare the predicted final heights with the actual measured heights at age 18.