Shielded metal arc welding (SMAW) has been the welding industry's mainstay and heavily used in construction. SMAW is governed by a large variety of factors, and so it is very difficult to gain expertise in SMAW procedures. This paper presents an expert system to help plan and train shielded metal arc welding (SMAW) operations. The expert system has been implemented in Prolog. It accumulates most of the available information on the SMAW process including edge preparation, electrode selection, economic evaluation, analysis of weld defects1 and trouble-shooting. The expert system also includes an ''planation subsystem, which will show the reasoning process to reach a conclusion.