The four main features of biological identity are sex, age, stature, and ethnic background. The forensic osteologist aims to establish these attributes for an individual from their skeletal remains. Many techniques are available for the osteological determination of sex in the adult but it is one of the most difficult biological factors to ascribe to juvenile remains. Conversely, there are a multitude of markers to estimate age in the young skeleton but ageing becomes less accurate with increasing years. Stature is usually a relatively straightforward parameter to establish in the adult. In the juvenile, it is naturally correlated with age but is complicated by differences in rates of growth both between the sexes and between individuals. Determination of ethnic identity is the least reliable and is hampered by lack of data on many populations. This paper reviews the principal methods used to establish identity and comments on their reliability and accuracy in the forensic context. Clin. Anat. 15:297–312, 2002. © 2002 Wiley-Liss, Inc.