The purpose of this study was to find out what school teachers know about Autism. In addition, this study attempted to find out if there any significant differences in school teachers' knowledge about Autism depending on teachers' (gender, position, education level, teaching experience, and contact with students with Autism) variables. A total of 391 general and special education teachers from various segregated and inclusive schools within the Jeddah in Saudi Arabia completed study instrument ("Autism Knowledge Questionnaire") to determine their level of knowledge about Autism. An analysis of the collected data, using descriptive statistics and analysis of variance, indicated that school teachers had an acceptable approaching to weak level of knowledge about Autism disorder. The results also indicated significant differences in the teachers' knowledge about Autism depending on teachers' (position, education level, teaching experience, and contact with students with Autism) favoring special education teachers, more advanced level of education and teaching experience, and those with previous contact with students with Autism.