REDUCE on a Massively Parallel System Winfried Neun Konrad--Zuse--Zentrum Berlin The implementation and usage of the Computer Algebra system REDUCE on a massively parallel system (in our case the Cray T3D) is discussed here. The aim of the implementation is to retain portablity among parallel systems by refraining from the usage of propriatary software solutitions. The communication protocol (using the Parallel Virtual Machine), the user interface and parallel extensions to the REDUCE command language are presented. The results of some typical computations in CA using this approach will be given.