This two-part article contains an in-depth analysis of a variety of convertible debt instruments from the perspective of international tax law. Part 1 covers optional convertible instruments, mandatory and reverse convertibles, contingent convertibles, warrants and option loans and provides an overview of domestic law in a number of countries. Part 2, to be published in European Taxation 5 (2017), analyses the classification and treatment of the different types of convertible debt instruments from the perspective of EU corporate tax directives and tax treaties.