The development of microarrays for the screening of gene expression has highlighted the importance of obtaining high quality RNA. We have investigated whether it was possible to obtain RNA of sufficiently good quality from postmortem human tissue using samples obtained from the New Zealand Neurological Foundation Human Brain Bank. We have investigated the effect of PM delay, the duration of the agonal state, the tissue pH, the age at death and the sex of the patient on the quality of normal human brain tissue and tissue from patients with various neurodegenerative conditions. Postmortem delay was shown to affect the RNA quality adversely, but the magnitude of the effect was small. While cerebellar RNA quality was not always an exact predictor of the RNA quality in other brain regions of interest, it was shown to have some predictive value and can be used as a preliminary indicator. The principle finding was that RNA quality is most strongly affected by the pH of the tissue, with both the pH and the RNA quality being influenced by the mode of death.