The relative contributions of factors operating in fetal life, childhood, and adulthood to risk of disease in middle age have become an important research issue, though oral health has rarely been considered. This study investigated the relative impacts of risk factors operating at different stages throughout life on the number of teeth retained at ages 49-51 yrs based on data from the Newcastle Thousand Families cohort. Very little variation in tooth retention in middle age was explained by factors operating at earlier stages in life. The previously noted relationship between childhood socio-economic status and oral health in adulthood appears, with respect to tooth retention, to diminish with increasing age as adult socio-economic position and lifestyle factors have an increasing effect. Promotion of a healthier adult lifestyle and continued improvements in oral hygiene would appear to be the public health interventions most likely to increase tooth retention in middle age.