The topic of this honours project is "A virtual memory technique for a BCPL compiler". BCPL is a high level language suitable for writing system software such as editors and compilers. It is available on the Computer Science Department’s Data General Eclipse S/130 computer. The compiler is written in BCPL. During a compilation the BCPL compiler creates a syntax tree and a symbol table in a work-space of fixed size. This places a limit on the size of a compilable BCPL program, which would be removed if a virtual memory technique for the storage of the syntax tree and the symbol table was to be implemented. The aim of this project was to investigate this possibility. The first step was to gain some knowledge of the working of the compiler by studying the code and to obtain some statistics by inserting probes into the compiler. Using the knowledge gained and by simulating various virtual memory techniques a paging algorithm was designed and implemented. This report begins with a brief overview of BCPL and a detailed statement of the problem. The studies, design, implementation, and results are then presented followed by a conclusion. The guidance of Dr M.A. Maclean, Project Supervisor, is gratefully acknowledged.