In study one, 163 adults with intellectual disabilities (ID) who chronically received psychotropic medications were evaluated to further establish psychometric properties of the Matson Evaluation of Drug Side-effects (MEDS). Test-retest reliability was also examined for 76 adults. Cutoff scores for total and subfactors are reported as well as the implications of the present data for evaluating antipsychotic medications. In study two of our paper, we explored drug prescription practices for the same 163 participants. While most participants had been switched to atypical antipsychotic drugs, akathisia and tardive dyskinesia were still typical and frequent side effects. The implication of the data in these studies is discussed with respect to using the MEDS as a means of assessing side effects resulting from chronic antipsychotic drug use.