Autism spectrum disorder is a neurodevelopmental disorder of unknown aetiology. It is suggested to involveboth genetic susceptibility and environmental factors including in the latter environmental toxins. Human ex-posure to the environmental toxin aluminium has been linked, if tentatively, to autism spectrum disorder. Hereinwe have used transversely heated graphite furnace atomic absorption spectrometry to measure, for thefirst time,the aluminium content of brain tissue from donors with a diagnosis of autism. We have also used an aluminium-selectivefluor to identify aluminium in brain tissue usingfluorescence microscopy. The aluminium content ofbrain tissue in autism was consistently high. The mean (standard deviation) aluminium content across all 5individuals for each lobe were 3.82(5.42), 2.30(2.00), 2.79(4.05) and 3.82(5.17)μg/g dry wt. for the occipital,frontal, temporal and parietal lobes respectively. These are some of the highest values for aluminium in humanbrain tissue yet recorded and one has to question why, for example, the aluminium content of the occipital lobeof a 15 year old boy would be 8.74 (11.59)μg/g dry wt.? Aluminium-selectivefluorescence microscopy was usedto identify aluminium in brain tissue in 10 donors. While aluminium was imaged associated with neurones itappeared to be present intracellularly in microglia-like cells and other inflammatory non-neuronal cells in themeninges, vasculature, grey and white matter. The pre-eminence of intracellular aluminium associated with non-neuronal cells was a standout observation in autism brain tissue and may offer clues as to both the origin of thebrain aluminium as well as a putative role in autism spectrum disorder.