The jury informed the court this afternoon it had failed to agree on a verdict on any of the counts against Ayres.
Judge Beth Freeman declared a mistrial shortly before 4 p.m.
Ayres, who was president of the American Academy of Child and Adolescent Psychiatry from 1993 to 1995, was charged with nine counts of lewd or lascivious acts on a child under 14. He would have faced up to life in prison if convicted.
The trial focused largely on physical exams Ayres conducted on his patients. The alleged victims claimed the doctor groped them, and while Ayres admitted to performing physical exams in which the boys were naked from the waist down, he testified that nothing inappropriate happened.
Defense attorney Doron Weinberg argued that the alleged victims' memory of events should be questioned because of the amount of time between when the alleged crimes took place and when they came forward with their claims -- years after the alleged molestations took place.
Prosecutor Melissa McKowan, however, said the witnesses' accounts were accurate and credible.