Drug-food interactions (DFI) occur when there is concomitant administration of a drug and a food that leads to an alteration in the kinetics or dynamics of the drug or nutrient, or the impairment of the nutritional status as a result of the administration of a drug. The elderly are at greatest risk of experiencing DFI, as they are more prone to chronic use of medications and polypharmacy. The objective this research is to determine the prevalence of potential drug-food interactions in the elderly using prescription drug. A cross-sectional study was conducted with 342 elderly serviced by a public primary care service. Potential drug-food interactions (PDFI) were identified through the MICROMEDEX ® Interaction database program. The prevalence of DFI was 58.5%, in a total of 278 potential interactions identified. Potential drug-food interactions most frequently occurred in patients who maintained a habit of eating and taking medication at the same time. Multivariate analysis revealed the increased chances of DFI with increasing amount of drugs in use by the elderly. Being diabetic and have poor knowledge about the use of drug therapy were also factors that increased the chance of occurrence of PDMI. The occurrence of DFI is more frequent than potential drug interactions. The drugs involved in most DFI are commonly used in the pharmacotherapy of diabetes and hypertension, and the factors that are associated with the occurrence of PDFI were the number of medications taken and the level of knowledge of the elderly about their pharmacotherapy.