STUDY OBJECTIVE--To compare the rates of reported emergency appendicectomies in a cohort study of vegetarians and non-vegetarians by participants' history of meat consumption. DESIGN--This was a prospective cohort study in which participants were asked about their lifetime history of meat consumption/avoidance and, separately, whether they had had an appendicectomy. Appendicectomy was described as either "emergency" or "non-emergency" according to details supplied by the participant. SETTING--The United Kingdom. PARTICIPANTS--These comprised more than 11000 people, of whom 4852 (44%) completed both an appendicectomy form and a dietary questionnaire giving details of their lifetime history of meat consumption. MAIN RESULTS--The percentage who reported an emergency appendicectomy was higher among lifelong meat eaters (10.7%) than either lifelong non-meat eaters (7.8%) or those who had stopped eating meat (8.0%); and the operations were performed at an earlier age in this first group (mean values 18.9, 26.0, and 19.6 years respectively). The overall age adjusted emergency participants who did not eat mean with those who ate meat was 0.47 (95% confidence interval 0.35, 0.65). CONCLUSION--The results suggests that people who do not eat meat have a 50% lower risk of requiring an emergency appendicectomy than those who do. The data do not, however, allow the reliable testing of other hypotheses, so meat consumption may simply be a marker for another dietary, lifestyle, or socioeconomic factor.