In many business, commercial and financial transactions (M&A, leasing, corporate financing, project finance, commercial lending, purchase order finance) one of the parties requires the other to procure a personal and/or corporate guarantees or to grant a security interest or security package over certain assets and/or rights to secure performance of its contractual obligations. And among many available options, the selection of the guarantees and securities to be granted, depends on many variables that need to be assessed carefully in order to choose the “best possible guarantee and security package” from a cost-benefit perspective. To that end, the parties must consider elements such as tax implications, costs associated with granting and maintaining the security package, enforcement costs, efficiency and efficacy of enforcement, effects of insolvency on the security, among other aspects. Based on the above, this course will focus in analyzing the main types of guarantees and securities used in business, commercial and financial transactions, and with respect to each one of them, a comparative analysis will be made to provide students with practical and legal tools to structure adequate guarantee packages in their own business and transactions.