The height and weight measurement of 928 young people of Busselton were collected over a period of up to 11 years. The prevalence of obesity was low in early childhood and increased progressively through adolescence and adulthood, so that 9% of male subjects and 16% of female subjects aged 21 years or over, were obese. The prevalence and degree of obesity were both greater in female subjects than in male subjects. Although most obese young adults were not obese in childhood, 50% of those who were obese between the ages of 9 and 14 years were still obese when examined in young adult life, and were at greater risk of becoming obese adults than were their non-obese peers. Most subjects who subsequently became obese young adults were significantly heavier than their non-obese peers at all ages from the age of 6 years.