Purpose: The age of the patients, the presence of one or more chronic disorders and the patients' drug regimens can influence dental treatment and oral health. This is a prospective, descriptive study to identify subjects with compromised health who received dental treatment between November 2010 and June 2011 at private dental practices run by graduates of the Portuguese Catholic University. Materials and Methods: Application software in Microsoft Excel was developed containing the questionnaire, based on the EMRRH (European medical risk related history), which allowed the collection of data from 1603 adult patients. Microsoft Excel, G*Power and SPSS V.18 were used for statistical treatment. Results: The five most frequent medical conditions found were: 1) hypertension, 21.0%; 2) arrhythmias, 11.2%; 3) Angina pectoris, 8.3%; 4) allergies, 77%; 5) thyroid disease, 6.2%. The medications taken related to these were: a) antihypertensives, 11.0%; b) antidepressants, anxiolytics and hypnotics, 10.6%; c) acetylsalicylic acid, 4.2%; d) antiarrhythmic and sympathomimetic drugs, 4.1%; e) haemostatic treatment, 3.6%. 42.7% of the patients had no medical risks, 32.9% were classified as ASA II, 11.7% as ASA III and 12.7% as ASA IV. Conclusion: This study emphasises the importance of often-neglected anamnesis in oral care. The high prevalence of patients with medical conditions should be continuously studied to verify the changes over time and should be expanded to other regions and countries. Keywords: dental health status, health risk, medically compromised patient