This is the first edition for nearly 150 years, taking into account a fuller range of manuscripts than either of the previous editions, of the collection of problems on natural science and medicine edited by Bussemaker in 1857 as pseudo-Aristotle, Problemata Inedita , and by Usener in 1859 as pseudo- Alexander of Aphrodisias, Problems books 3 and 4, the attribution differing in different manuscripts. The new critical text, based on collation of 31 Greek manuscripts, is accompanied by an annotated English translation. An extensive introduction reconstructs the complex manuscript tradition and examines the origin and nature of the collection, which is argued to be complex, including