OBJECTIVE i) To develop a measure of the impact of fixed orthodontic appliances on daily life. ii) To assess the impact of fixed appliances over time after initial appliance placement. iii) To investigate factors that may influence the impact of fixed appliances (age, gender and socioeconomic status). METHODS Questionnaire. METHODS University Dental Hospital and Hope Hospital, Manchester. METHODS Sixty-six patients, whose orthodontic appliances had just been placed. Twenty-eight patients whose orthodontic appliances were in place for at least six months were used for the reliability study. METHODS The Impact of Fixed Appliances Questionnaire was developed using standard qualitative methods and pre-tested on 10 patients. This resulted in a questionnaire with nine conceptual impact sub-scales: aesthetic, functional limitation, dietary, oral hygiene, maintenance, physical, social, time constraints and travel/cost. The questionnaire was piloted on 66 patients, at the first, second and third visits after their fixed appliance had been placed, to assess the impact of fixed appliances over time. Questionnaire reliability, over a one-month time interval, was assessed on 40 patients who had been in treatment for at least six months. METHODS Impact of fixed appliances on daily life. RESULTS The internal reliability of the questionnaire ranged from moderate to very good (Cronbach's alpha 0.56-0.89). Test-retest reliability was stable for most subscales (intra-class correlation coefficient 0.26-0.65). The questionnaire was said to have face validity and also content validity because of the method of questionnaire development through interviewing children with fixed appliances. None of the subscales scores reduced over time except aesthetic impact (p< 0.05) but this was probably not a clinically significant change. Age was the predominant variable to influence the impact of fixed appliances with younger children being less affected during their daily life (p<0.05). CONCLUSIONS The questionnaire developed in this study is a reliable tool for assessing the impact of fixed appliances on the daily life of children. It is unlikely that the impact of fixed appliances on daily life reduces as the patient progresses through treatment. Younger patients are probably more adaptable to treatment with fixed appliances, in terms of reduced impact on daily life, so arguably treatment should be started as early as possible. This information could also be used to educate, reassure and motivate patients at the start of treatment.