Increasingly, men and women are deciding against starting families. The resulting ageing of the population has major implications for social policy. What reasons are people giving for not having children? Have the reasons changed since the early 1980s, and do these differ according to age? These issues are explored in this article drawing on data from two surveys conducted by the Australian Institute of Family Studies 15 years apart - the Australian Family Formation Study conducted in 1981 and the Australian Life Course Study conducted in 1996.