This book constitutes the refereed proceedings of the 4th International Symposium on Logical Foundations of Computer Science, LFCS'97, held in Yaroslavl, Russia, in July 1997. The volume presents 42 revised refereed papers carefully selected by the program committee. All current issues of computer science logic are addressed. There is a certain emphasis on reporting the progress achieved by scientists from various parts of the former Soviet Union; but there are also many other strong papers from the international research community.