ITT has developed and implemented a flexible CAD system strategy which solves major problems in integrating VLSI design aids. The complexity of current generation VLSI CAD and the proliferation of commercial and internally generated design aids necessitates a coordinated approach to CAD system integration. This need was recognized early at ITT where it is compounded by a multi-national design environment comprising 14 major VLSI design centers and a growing number of smaller design centers each with its own specific set of needs and constraints. The CAD system integration strategy described achieves flexibility through a neutral data format tool interface architecture, a software language standard, and multi-source-able design rules. The paper describes the strategy and the semi-custom and full custom design systems developed following the strategy.