During play encounters dogs vocalize using at least four distinct patterns; barks, growls, whines, and a breathy pronounced forced exhalation (dog-laugh) (Simonet, 2001). Further, dog-laughs are used to initiate play. Upon hearing a dog-laugh subjects use a play- face and chase or play-bow with the individual producing the dog-laugh, whether the individual is dog or human (Simonet, 2001). This study employs a recorded playback of the dog-laugh vocalization, investigating how this vocalization ameliorates dog stress upon entry to and duration of stay at a mid-size county animal shelter. Stress is measured by an ethogram of behaviors (including, panting, salivating, pacing, barking, cowering, lunging, play-bows, sitting, orienting, and lying down) and by recording the ambient noise level of the kennel. This experiment uses a within subjects cross-over design comparing the same dogs to themselves in two different conditions; baseline condition - no playback, and the experimental condition - playback. Dogs experienced a significant reduction of stress behaviors during dog-laugh playback. In addition, during the experimental condition dogs expressed an increase in pro-social behaviors such as, approach and lip licking (Bekoff & Allen, 1998). This study suggests that the dog-laugh vocalization diffuses stress related behavior and initiates pro-social behavior in shelter dogs, thus potentially reducing residency time.