Patients diagnosed with Autism Spectrum Disorder, show impaired integration of information across different senses. The processing-level from which this impairment originates, however, remains unclear. We investigated low-level integration of auditory and visual stimuli in subjects with Autism Spectrum Disorder. High-functioning adult subjects with Autism Spectrum Disorder as well as age- and IQ-matched adults were tested using a task that evokes illusory visual stimuli, by presenting sounds concurrently with visual flashes. In both groups the number of sounds presented significantly affected the number of flashes perceived, yet there was no difference between groups. This finding implicates that any problems arising from integrating auditory and visual information must stem from higher processing stages in high-functioning adults with Autism Spectrum Disorder.