The aim of the study was to develop a system supporting technological process planning, the functioning of which would resemble the way  human experts act in their fields of expertise, one capable of gathering necessary knowledge, analysing data, and drawing conclusions to solve problems. This could be done by utilising artificial intelligence (AI) methods available within such systems. The study proved the usefulness of AI methods, and their significant effectiveness in supporting technological process planning. Technological process planning based on an expert system is divided into the following stages: the selection of the semi-finished products; the establishing of the technological process structure, and the selection of the workpiece instrumentation, machine tools, other tools, and tooling and machining parameters for each technological operation. The system-embedded knowledge takes the form of neural networks, decision trees and facts. The system is presented using the example of a real enterprise.