The authors assessed the reliability of the Autism Diagnostic Interview (ADI-R). Seven Clinical Examiners evaluated a three and one half year old female toddler suspected of being on the Autism Spectrum. Examiners showed agreement levels of 94-96% across all items, with weighted kappa (K[subscript w]) between 0.80 and 0.88. They were in 100% agreement on 74% of the items; in excellent agreement on 6% of the items (93-96%, with K[subscript w] between 0.78 and 0.85); in good agreement on 7% (89-90%, with K[subscript w] between 0.62 and 0.68); and in fair agreement on 3% (82 - 84%, with K[subscript w] between 0.40 and 0.47). For the remaining 10% of ADI-R items, examiners showed poor agreement (50-81% with K[subscript w] between -0.67 and 0.37).