Josef Helfenstein took over as head of the Paul-Klee-Stiftung [Paul Klee Foundation] following Jürgen Glaesemer’s sudden and untimely death in 1988. His period in office (1988–2000) was marked first and foremost by the project for the Catalogue raisonné Paul Klee and by the development of the electronic Klee database.

Preparations for the Catalogue raisonné Project began in earnest in 1988 under Stefan Frey as the project manager, based on earlier preliminary work. Production began in 1998 and lasted until 2004. A Klee database was subsequently developed under the project management of Christian Rümelin (who worked for the Paul-Klee-Stiftung from 1996 to 2002). It proved such a pioneering tool that it went on to provide the basis for a museum database, which is today used in many large European museums.

The Paul-Klee-Stiftung’s exhibition activities and other services continued alongside the work on the Catalogue raisonné Paul Klee. Besides advising and personally assisting scientists, and loaning exhibits from its own collection the Paul-Klee-Stiftung also provided expertises of works and, as the only such institution worldwide, issued certificates of authenticity for works by Paul Klee.