The Polish alchemist Michael Sendivogius is best known for the influential Novum lumen chymicum, a work composed of three separate texts. Sendivogius's authorship was questioned in the mid-seventeenth century, and these reservations are still held by some modern historians. On the other hand, other early modern and modern readers not only accepted his authorship of all three texts, but also ascribed as many as eleven texts to him. This paper discusses the key works published under the anagrammatised name of Sendivogius with the aim of resolving the authorship question. Newly discovered evidence makes it possible to trace the circumstances leading to the publication of these works in much greater detail than previously, and to present new arguments affirming Sendivogius's authorship. In the Tractatus de sulphure, Sendivogius promised to write another two treatises, which readers sought to identify and (in some cases) to write themselves. This paper sets out, and rejects, the arguments for including them in the corpus of genuine Sendivogian writings.