The realistic animation of the behavior of virtual agents emulating human beings and evolving within virtual 3D worlds (a field also known as Artificial Life) has received great attention during the last few years. The current challenge is to create a behavioral system for the virtual agents so that they behave as realistic as possible. Such a system should provide the agents with the most typical features of human intelligence: perception, recognition, memory, learning, reasoning, etc. Among the large number of different techniques to solve this problem, those based on Artificial Intelligence (AI) seem to be especially suitable for this purpose. In this paper, we apply several Artificial Intelligence techniques (such as neural networks, expert systems, fuzzy logic, K-means) to create a sophisticated behavioral system that allows the agents to take intelligent decisions by themselves. The paper describes the behavioral system, its main components and how these AI techniques have been effectively incorporated into the system. In order to show the good performance of our approach, an illustrative example will also be carefully analyzed.