This preliminary study examined the effects of 10 weekly lessons of therapeutic horseback riding (THR) on 42 participants diagnosed with an autism spectrum disorder (ages 6-16 years) compared to a subset (n=16) of the total study population who were first evaluated before and after a 10-week waitlist control condition. All participants received baseline and post-condition assessments in the areas of self-regulation (Irritability, Lethargy, Stereotypic Behavior, and Hyperactivity), adaptive living skills, and motor skills. Participants who completed 10 weeks of THR demonstrated significant improvements on measures of Irritability, Lethargy, Stereotypic Behavior, Hyperactivity, expressive language skills, motor skills, and verbal praxis/motor planning skills. When compared to the pre- and post-assessments of participants from the waitlist control condition, the THR group still showed significant improvements in self-regulation behaviors. The THR-specific change from the baseline to post-assessments suggests that the improvements are related to the THR treatment. (Contains 3 tables and 3 figures.)