Magister Chirurgiae Dentium (MChD) / The psychological, social, and cultural aspects of facial and dental attractiveness is an integral part of health care. Lay persons perceptions of facial and dental attractiveness are influenced by many factors including age, gender, geographic location (nationally or international), ethnic status, employment status, cultural differences and social class will effect the social impact of the anomalies. In addition, the public response to dental anomalies will vary according to experience of good health or ill health of the individual, relatives and friends. The perception of malocclusion is often seen differently between orthodontists, patients and lay public. The differing perceptions of patients and dental practitioners may influence the delivery of orthodontic care. It has been reported that 70% of orthodontic treatment is dentist induced and that orthodontic treatment may be undertaken without the patient or parents perceiving a problem with the teeth. (DHSS, Schanscheiff Report, 1986). The thresholds of entry and exit for orthodontic care may be different as perceived by orthodontists and lay persons. Orthodontists may pursue full alignment and perfect occlusion whereas lay persons may accept varying degrees of deviation from normal. This current study has assessed and recorded the differences in opinions of professional orthodontists and lay persons on dento-facial aesthetics, orthodontic treatment need and orthodontic treatment outcome. The study was carried out at the Orthodontic Department, University of Wales, College of Medicine, School of Dentistry. The opinions of 56 lay persons (dental technicians, dental nurses and lay persons not involved in the clinical process) and 97 orthodontists was collected by recording judgements using various patient records as stimuli. For each set of records examined, each member of the panel indicated their opinion using Likert scales. Judgements were made by assessments of 68 study casts in respect of:- * the need for orthodontic treatment on dental health grounds. the need for orthodontic treatment on dental aesthetic grounds. deviation from normal occlusion. the decision whether to treat. ** * In addition, judgements were made on a sample of 50 pairs of outline facial profiles before and after treatment in respect of: * * deviation from normal facial aesthetics comparison of aesthetics pre-treatment and post-treatment. Furthermore, assessments on 50 pairs of pre-treatment and post-treatment study casts in respect of: * * degree of improvement as a result of treatment. acceptability of result. Orthodontists subjective judgements are more reliable than lay persons in their assessments of dental aesthetics, dental health and deviation from normal. The level of agreement for the decision to recommend treatment is similar between orthodontists and lay groups ie. lay persons are as reliable as orthodontists in the decision to recommend treatment. Orthodontists tend to recommend 10 - 12 % more treatment than lay persons. The orthodontist group were more reliable than the lay group in assessing degree of improvement and assessment of outcome. Orthodontists reject approximately 25% of cases deemed acceptable by the lay group. Dental aesthetics appeared to be the most important feature in the assessment of treatment outcome by both orthodontists and lay groups.