The article presents the development of an expert system for decision support on the Android platform. To create a knowledge base, a medical subject area was chosen using the example of determining the risk of coronary heart disease in a practically healthy person. The main and additional risk factors for coronary heart disease were identified, which determined the hierarchical structure of the knowledge base. The knowledge base structure contains knowledge clusters so that the user can consult with the expert system depending on the choice of clusters. The knowledge base was implemented using the KARKAS shell, which has tools for creating expert systems: a visual knowledge base editor, a knowledge base parser, a hierarchical functional system for forming a knowledge base structure based on rules and frames, and various modules for implementing logical conclusions.