The chapter presents decision support systems in medicine, their basic principles, and structure. From the point of view of patient safety, the decision support systems can bring new unexpected sources of errors, which must be anticipated at the design, implementation, and validation stages. Nevertheless, a safe and easy-to-use system can greatly improve the quality of determining the diagnosis, prognosis, and therapy in healthcare. The authors of this chapter concentrate on the contribution of decision support systems to patient safety and on their potential to future contributions. A decision support system requires a user-friendly interface with the electronic health record and information system within the healthcare facility. The authors also present two examples of decision support systems from the genetics research.