Purpose:   To study a new, investigational treatment to reduce chronic gastrointestinal problems in children with ASD. 

Who can enroll?  Children with ASD ages 5-17 years who also have chronic constipation, diarrhea, and/or similar gut problems

Treatment:  The treatment involves 14 days of a special antibiotic, then a bowel cleanse, and then swallowing pills containing purified microbiota from healthy donors for 12 weeks.

Placebo-Controlled:  In Part 1, half of the participants will receive the real treatment, and half will receive a placebo (inactive).  Then, the placebo group will be switched to the real treatment in Part 2.

Duration: Part 1 lasts approximately 14 weeks, and Part 2 lasts another 14 weeks.  There are also follow-up evaluations at 6, 12, and 18 months after Part 2.  The study involves 2-3 visits to the clinic in Arizona, for 1-2 days each.