Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social communication and restricted or repetitive behaviors. Individuals with ASD often experience secondary difficulties in academic, daily living, and motor domains, further expanding the meaning of “spectrum.” As the global prevalence of ASD continues to increase, selecting effective interventions has become a critical priority. In evidence-based autism research, performance criteria are considered a key element in determining intervention effectiveness and whether behavioral change is socially meaningful. Performance criteria are predetermined levels of behavioral change that define when an intervention has produced a meaningful outcome. They consist of two main components: the desired level of behavioral change and the frequency with which this level must be demonstrated. The level component reflects the magnitude of behavioral improvement (or decrease), while frequency represents the consistency of this change across sessions. This chapter explains how performance criteria are structured and operationalized through examples from behavioral, educational, and medical studies. By accurately defining performance criteria, researchers can more reliably determine whether an intervention produces socially meaningful behavioral changes. Consequently, careful consideration of performance criteria strengthens the methodological rigor of autism research and supports the development of truly evidence-based practices.