This document provides a complete list of procedures and special forms implemented in version 3.1 of STK. Since STK is (nearly) compliant with the language described in the Revised4 Report on the Algorithmic Language Scheme ndexfile(index-entry "R4RS" "rm" main )(denoted R4RS hereafter1)[#!R4RS!#], the organization of this manual follows the R4RS and only describes extensions.