This thesis evaluated the measurement and enhancement of rapport between behavioral therapists and children with autism. The study defined rapport based on observable behaviors and assessed existing rapport levels between therapist-child dyads. It then evaluated an operant discrimination training procedure to enhance rapport for dyads with low initial levels. Results showed the training successfully conditioned social interaction as a reinforcer, increasing rapport as measured by behaviors like eye contact and smiles. This study provided an objective method for defining and measuring rapport, and demonstrated how a discrimination training procedure could strengthen rapport between therapists and children with autism.