The use of anti-epileptic medications (AEDs) is much higher in individuals with intellectual disabilities than in the general population. As many of these individuals rely on such medications, clinicians should consider psychometrically sound instruments for assessing adverse side effects of these medications as one aspect of routine clinical practice. The Scale for the Evaluation and Identification of Seizures, Epilepsy, and Anticonvulsant Side Effects-B (SEIZES B) was developed as a means to identify side effects specific to AEDs. The authors conducted a preliminary evaluation of the inter-rater and test-retest reliability of the SEIZES B on an adult population with developmental disabilities. The SEIZES B had moderately high stability across raters and adequate stability over time. Implications of these data for future research and practice are discussed.