CharSets is a Maple package developed by Dongming Wang on the basis of Wu-Ritt’s method of characteristic sets. The first version CharSets 1.0 was made publicly available with Maple’s share library in early 1991. Three subsequent versions 1.1, 1.2, and 2.0 were also distributed. The current version is CharSets 2.2. The early versions of CharSets were implemented for computing characteristic sets and various zero decompositions of polynomial systems and other related polynomial calculations. Their capabilities include: computing (modified) characteristic sets of polynomial sets (in different senses), decomposing polynomial sets into ascending sets and into irreducible and quasi-irreducible ascending sets, decomposing algebraic varieties into irreducible components, decomposing polynomial ideals into primary components, solving systems of polynomial equations, and factorizing multivariate polynomials over algebraic extension fields. A new module has been added to CharSets (since version 2.0) that contains eight functions for computing differential characteristic sets and the corresponding zero decompositions for systems of ordinary differential polynomials. Some of the routines from the CharSets package are used by the provers in GEOTHER, an environment for geometric theorem proving.