OBJECTIVE: To compare the prevalence of disease and drug consumption obtained by using the National Health Survey (NHS) with the information provided by the electronic medical records (EMR) in primary health care and the Pharmaceutical Consumption Registry in Aragon (Farmasalud) in the adult population in the province of Zaragoza.METHODS: A cross-sectional study was performed to compare the prevalence of diseases in the NHS-2006 and in the EMR. The prevalence of drug consumption was obtained from the NHS-2006 and Farmasalud. Estimations using each database were compared with their 95% confidence intervals (95% CI) and the results were stratified by gender and age groups. The comparability of the databases was tested.RESULTS: According to the NHS, a total of 81.8% of the adults in the province of Zaragoza visited a physician in 2006. According to the EMR, 61.4% of adults visited a primary care physician. The most prevalent disease in both databases was hypertension (NHS: 21.5%, 95% CI: 19.4-23.9; EMR: 21.6%, 95% CI: 21.3-21.8). The greatest differences between the NHS and EMR was observed in the prevalence of depression, anxiety, and other mental illnesses (NHS: 10.9%; EMR: 26.6%). The most widely consumed drugs were analgesics The prevalence of drug consumption differed in the two databases, with the greatest differences being found in pain medication (NHS: 23.3%; Farmasalud: 63.8%) and antibiotics (NHS: 3.4%; Farmasalud: 41.7%). These differences persisted after we stratified by gender and were especially important in the group aged more than 75 years.CONCLUSIONS: The prevalence of morbidity and drug consumption differed depending on the database employed. The use of different databases is recommended to estimate real prevalences.