The paper discusses the development of decision- making software for patients with kidney stones. Computerized decision–making about treatment choices for patients with renal stones is step-by-step described in this paper. Medicine is one of the sectors where computerized decision-making is being used more often. One of the key elements of expert systems – building a knowledge base that is based on recommendation fund, known as „Guidelines”, is discussed. The paper discusses the most frequently used therapies. Examples of decision trees and production rules are shown.