Autism spectrum disorder (ASD) is characterized by deficits in social interactions and communication, and restricted and stereotypic behaviors. A growing body of evidence has identified metabolic pathways and glutamatergic neuro-transmission affecting oxidative stress levels as potential targets of drug development in autism spectrum disorders. N-acetylcysteine (NAC) is an antioxidant that modulate glutamate and reduce oxidative stress, both associated with the pathophysiology of ASD. N-acetylcysteine has been identified as a potential treatment agent for irritability and self-injurious behaviors in autism. In this case report, we report six cases of autism with severe symptoms of irrita-bility and aggression, two of them responded well to N-acetylcysteine treatment, two of them responded partially and while two did not. [Anadolu Psikiyatri Derg 2020; 21(2.000): 218-221]