SFILES is a program for entering molecular structures and storing them in a connection table form on a disk file for later use in Quantitative Structure Activity Relationship studies (QSAR). The user may enter a structure by drawing its hydrogen suppressed representation on a TEKTRONIX 4014 or compatible graphics terminal; or by building the connection table via one of two terminal independent structure entry systems. The graphical method of structure entry is the default method used in the program, and is the method which allows the user the most versatility in structure entry. Use of the graphical method is described in the main part of this user's guide. The two terminal independent structure entry methods, SMILES and SENTRY, are described in Appendices A and B respectively of this user's guide. Implementation of the SENTRY method is not yet complete. It is anticipated that the implementation will be completed and Appendix B available by December 1984.