Objectives: To determine the prevalence and aetiology of systemic disease among patients requesting dental treatment in public and private practice. Study Design: A retrospective analysis was performed of the medical histories of 2000 patients requesting dental treatment during the year 2009. One thousand patients came from the Fontiñas Primary Care Oral and Dental Health Unit of the Galician Health Service (SERGAS), Spain, and the other thousand from a private clinic; both clinics were situated in Santiago de Compostela, La Coruña, Spain. The data collected were the following: demographic data (age and sex), presence or absence of systemic diseases and the nosologic categories, and drug history (type and number of drugs). Results: The prevalence of systemic disease was significantly higher among patients seen in the public system (35.2% in the public system versus 28.1% in the private system; p= 0.003). The differences between the two systems were more marked when considering patients aged under 65 years, particularly with respect to rheumatic and endocrine-metabolic (diabetes) disorders. The prevalence of patients receiving polypharmacy (>4 drugs/day) was significantly higher among patients seen in the public system (5.7% in the public system versus 2.7% in the private system; p= 0.009). Conclusions: There is a high prevalence of medical disorders and of patients receiving polypharmacy among individuals requesting dental care, particularly in the public health system. Dentists must have adequate training in medical disease and must be fully integrated into primary care health teams in order to prevent or adequately resolve complications. © Medicina Oral S. L.