The Lisa Toolkit was a wonderful program development framework which gave Lisa developers a very powerful tool in making Lisa Office System programs. Based on an object-oriented derivative of Apple’s Lisa Pascal language called Clascal, the Toolkit provided a large class library which encapsulated the majority of the Lisa Office System’s core feature set. The Toolkit was later converted into MacApp for the Macintosh and Clascal was converted into Macintosh Object Pascal . These papers provide some basic information about the Toolkit’s architecture and the Clascal language. The key person behind the Toolkit was Larry Tesler who also headed the Lisa Office System development.