This proceedings, Robotics 98, contains papers presented at Third Specialty Conference on Robotics for Challenging Environments held in conjunction with the Sixth International Conference on Engineering, Construction, and Operations in Space in Albuquerque, New Mexico, from April 26-30, 1998. This third conference continues efforts to bring together researchers working on robotic technologies and those seeking to apply these technologies in a variety of challenging environments. The papers cover such topics as: design and control of flexible manipulators; path planning for mobile robots; sensing and modeling of unknown environments; applications in hazardous environments on Earth; applications in construction; mobile systems and rovers; robotics in education; operator interfaces; and technology transfer. It is the hope that this proceedings will help foster communication between researchers who might not be aware of each other's work, so that knowledge and experience gained in one domain may be applied to another.