Objective: The aim of the present study is to investigate whether brain metabolism of boys with autism spectrum disorder (ASD) is altered compared to boys with a developmental delay without autism if corrected for patient age and developmental level. Study design: 25 boys with ASD (with or without concurrent mental retardation) and 12 boys without ASD with mental retardation or language disorder underwent proton magnetic resonance spectroscopy. All analyses were performed with chronological age and developmental level as independent variables. Results: No metabolic differences were found between boys with ASD and without ASD. Conclusions: Our findings do not replicate previous reports of differences in NAA, Cho and Cr levels in ASD.