Solving complex decision problems sometimes requires using extensive tree like data structures to represent the relationships among the variables involved in the problem. Once generated, this structure must be analyzed. It is onerous task to generate and evaluate larger trees by hand. This thesis provides a presentation of Decision Tree System that the Decision Analysis Group has developed for describing and analyzing decision trees. Dynamic, uncertain, and complex decision situations are characterized. The importance of decision trees is emphasized through the overview of decision analysis. With concepts of tree-like data structures, the development of Decision Tree System is given.