This volume contains the papers accepted for presentation atthe Fourth International Symposium on Programming LanguageImplementation and Logic Programming (PLILP '92) held inLeuven, Belgium, August 26-28, 1992. Theaim of the symposium was to explore new declarativeconcepts, methods and techniques relevant for implementationof all kinds of programming languages, whether algorithmicor declarative. The symposium gathered researchers fromthe fields of algorithmic programming languages as well aslogic, functional, and object-oriented programming. The topics discussed in the volume include:- Declarative implementation techniques;- Implementation of declarative concepts and modules;- Compiler specification and construction;- Program transformation;- Programming environments for declarative languages;- Amalgamation of logic programming with algorithmic,functional, or object-oriented techniques;- Executable specification.