Historical documents indicate that breastfeeding and weaning practices have fluctuated in England through history. In order to obtain evidence for general breastfeeding patterns in Late/Sub-Roman Britain, stable carbon and nitrogen isotope values were measured in juvenile and adult skeletons (n = 87) from the cemetery of Queenford Farm, Dorchester-on-Thames, Oxfordshire. As the site contained few individuals between 0–1.5 years of age, it was not possible to determine the initial timing for the introduction of weaning foods. Between ages 2–4 years, the mean ± SD δ13C results (−20.2 ± 0.3‰) are significantly more negative (t = −4.03, P < 0.001) compared to adult females (−19.7 ± 0.3‰). This is interpreted as evidence of a different diet being fed to children during weaning. After age 2, the δ15N values gradually decline, indicating complete cessation of breastfeeding by 3–4 years. Among adults, stature (males = 1.68 ± 0.06 m; females = 1.58 ± 0.07 m) and sexual dimorphism (106) were low, suggesting that the population was possibly under environmental stress. The δ13C results for adults are similar, but females show a small but statistically significantly (t = −2.86, P < 0.01) lower mean δ15N value (9.9 ± 0.9‰) compared to males (10.6 ± 0.5‰). These lower female δ15N values possibly reflect the different physiology of the sexes (pregnancy and/or lactation) or the reduced consumption of animal/fish protein by women, and this may have been influenced by individual preference, family needs, or societal values of the era. Am J Phys Anthropol, 2006. © 2005 Wiley-Liss, Inc.