This manual describes Version 4 of Soar, an architecture for problem solving and learning based on heuristic search and chunking. Version 4 is available as of January 1986 in Common Lisp, Franz-Lisp, Interlisp, and Zeta-Lisp. An introduction to the Soar system is presented, and information is provided about the following system aspects: (1) data representation in working memory; (2) production representation; (3) decision procedure; (4) subgoals; (5) default search control; (6) chunking; (7) encoding a task; (8) operator implementation goal tests and operator parallelism; (9) top-level variables and functions; (10) errors, warnings, and recovery hints; and (11) the installation of Soar. Also provided are a performance comparison of the time required to solve a simple problem in the Eight Puzzle on different Lisp systems in Version 4, release 1; a brief annotated Soar bibliography; and a distribution list for this report. Two appendices contain a list of search-control productions and a summary of functions and variables, and an index is provided. (KM)