A growing body of research has raised concerns about the number of individuals diagnosed with autism spectrum disorder (ASD) according to DSM-IV-TR who may no longer qualify for diagnoses under the new DSM-5 criteria, published in May 2013. The current study systematically reviews 25 articles evaluating samples according to both DSM-IV-TR and DSM-5 ASD criteria. Consistent with previous reviews, the majority of included studies indicated between 50 and 75% of individuals will maintain diagnoses. We conducted visual analyses of subgroups using harvest plots and found the greatest decreases among high-functioning populations with IQs over 70 and/or previous diagnoses of PDD-NOS or Asperger's disorder. We discuss the potential research and clinical implications of reduced numbers of individuals diagnosed with ASD.