Children with Autism Spectrum Disorders (ASD) have difficulties engaging in imitation behavior. Available clinical tests that evaluate imitation rely on subjective observation and categorical 'yes' or 'no' data. We describe the development of a method to quantify imitation using a robot, kinematic data and a Dynamic Time Warping algorithm. A realistic-looking robot performed movements such as 'waving hello/goodbye', 'good job fist bump' and encouraged children with ASD and controls to imitate it. Preliminary results show that children with ASD interact positively with the robot and the DTW similarity measure may serve as both a meaningful and objective tool for evaluating the quality of imitation behavior.