We utilized nylon arrays to measure gene expression in mouse brains after various postmortem intervals (PMIs). Gene expression after overnight refrigeration or 4 h at room temperature then overnight refrigeration correlated highly and approximately equivalently to that in brains processed immediately. After 8-24 h at room temperature and overnight refrigeration gene expression correlation and equivalency declined, but 90-95% of detected genes were within +/-40% of baseline levels. Brain homogenate pH did not change with PMI.