To describe patients knowledge of non-opioid analgesics (NOA) and to identify factors associated with patients lack of basic knowledge (LBN) on this type of medication. A total of 629 ambulatory patients older than 50 years of age, with non-malignant pain syndrome, attended to two family medicine clinics and received seven day prescriptions for NOA. The data on patients general characteristics, the information they received and their actual knowledge of NOA were analyzed using descriptive statistics and bivariate analysis. A total of 64.2% had LBN; 28% did not know how to take NOA properly, and 48% knew that these drugs cause gastrointestinal adverse effects. The factors significantly associated with LBN on NOA included: failure to receive information on NOA (OR:2.22, 95%CI 1.32-3.70), education