The skeletal remains of infants and children are a poignant reminder of the perilous nature of childhood in the past, yet they offer valuable insight into the life histories of individuals and into the health of populations. Many osteoarchaeological and bioarchaeological analyses are dependent on two vital pieces of information: the age-at-death and sex of the individual(s) under study. This chapter will outline how age-at-death and sex can be estimated from the skeletal remains and dental development of non-adults, and how these are easier or more difficult to determine than for adults, and will discuss the complexities and controversies surrounding different methods.