The need for special Al hardware architectures arises out of support requirements imposed by Al languages. LISP - the language of choice for most Al research and development in the United States - is, in general, poorly served by today's conventional computer architec-tures. To better understand the architectures that will support the Space Station program, Al languages are examined and resulting architecture requirements are discussed. Generic parts required in these special Al architectures are presented, beginning with simple block diagrams and including discussion of their functions. Current and future LISP machine architectures are discussed and a current LISP machine workstation, the Explorer, is examined. The Compact LISP Machine, an embedded com-puter being developed with DARPA funding, is reviewed. Finally, higher functionality uniprocessor LISP machines, the potential for RISCs (reduced instruction set computers), and multiprocessor Al machines are briefly considered.