Problem: The nature of the peptides found increased in urine from autism needs verification of their structure, especially those that show opioid activity. Methods: The peptides were separated on reverse phase C-18 HPLC in Trifluoroacetic acid–acetonitril gradients. Peaks eluting where synthetic opioids appear, and peaks that are common to most autistic children were analyzed by mass spectrometry and fragmentation pattern on a quadropole mass-spectrometer. Results: We could demonstrate exorphins in the urine from autistic children, and their length varied from one patient to the next. Conclusion: Exorphins are found in urine of autistic children and may account for their symptoms.