Autonomous robots need the ability to move purposefully and without human intervention in real-world environments that have not been specifically engineered for them. These environments are characterized by the pervasive presence of uncertainty: the need to cope with this uncertainty constitutes a major challenge for autonomous robots. In this note, we discuss this challenge, and present some specific solutions based on our experience on the use of fuzzy logic in mobile robots. We focus on three issues: how to realize robust motion control; how to flexibly execute navigation plans; and how to approximately estimate the robot's location.