Introduction: The written information on medicines has been acknowledged as an important tool for health education. Objective: To analyze the use and understanding of medicine package inserts by users and assess sociodemographic and medical factors associated with their comprehension. Method: Data in this analysis are part of the PNAUM National Survey - a cross-sectional population-based study conducted in Brazil. Descriptive statistics and the Pearson χ2 tests were performed to compare proportions between sociodemographic and medical characteristics, as well as use and understanding of medicine package inserts. Results: A total of 28.427 individuals responded to questions related to medicine package inserts. From these, 59.6% (95%CI 57.7 - 61.5) said they usually read the inserts, and 98.4% (95%CI 98.0 - 98.8) considered them necessary. Among people who read the medicine package inserts, more than half indicated difficulties with legibility (57.4%; 95%CI 55,2 - 59,6) and readability (54.1%; 95%CI 52.1 - 56.1). People from a lower education level reported greater difficulty in understanding them. Conclusion: The larger portion of the population usually read medicine package inserts. Nevertheless, people have difficulty in reading and understanding them.