This paper describes the design and implementation of a robotic system for interaction with children with autism spectrum disorders (ASD). The system consists of a robot and supporting infrastructure, including a “smart room”. The intent of this work is to explore and study the design of a therapeutic, minimally-restrictive environment that enables free-form human-human and human-robot interaction. Our primary design goals include: 1) using minimal structure with the participants in order to elicit natural behavior; 2) increasing a child’s social interactions while utilizing minimal human-operated technology; and 3) facilitating human-robot interaction while requiring the child to wear no more than the minimum needed for effective signal detection. The robot system implemented in this study uses non-invasive methods for sensing and interpreting the child's behavior in order to interact with a child in free-form play while eliciting social behavior from the child. We present results from two feasibility studies with 12 children with ASD in order to validate the effectiveness of the robot system. We also discuss recommendations for the use of robot technology in ASD research settings.