This book explores the practical and experimental aspects of in vitro drug release assays, focusing on technical details. It presents examples of in vitro release assays performed with drugs encapsulated in nanostructured systems such as nanoemulsions, nanoemulgels, liposomes, solid lipid nanoparticles, and polymeric nanocapsules. The apparatus used, the composition of receptor media, and the types of membranes employed in these experiments are described in detail. Additionally, the mathematical treatment of raw data generated during drug quantification is discussed to ensure reliable results. The application of kinetic models to describe release profiles is also examined, providing insight into the mechanisms behind controlled drug release. This content is intended for researchers, students, and professionals in the chemical and pharmaceutical fields. The work was developed as part of the course Topics in Physical Chemistry III on the theme Kinetic Models of In Vitro Release of Nanoencapsulated Drugs, within the Postgraduate Program in Chemistry at the Federal University of Ceará (UFC). This project was financially supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) through the Programa de Excelência Acadêmica (PROEX), Brazil.