Recently, high fish intake or dietary supplementation with n-3 fatty acids has been linked to reductions in the risk of developing Alzheimer��s disease,, and to delayed cognitive decline in patients with very mild AD. N-3 FA are considered to exert the anti-inflammatory effects on several cellular levels, including surface receptor modulation, ion pumps, G-proteins, binding to transcription factors, as well as on gene activation. Previous investigations on effects of DHA and/or EPA on gene expressions in animal studies and in vitro models have shown changes in a variety of genes, some of which are believed to be involved in inflammation and chronic neurodegenerative disorder. These gene expression studies have mostly been conducted after a short time exposure and on small sets of genes,,,. However, a microarray study on the cerebral cortex of neonate baboon after 10�C12 weeks on a DHA-enriched formula showed changes in approximately 1000 probesets/genes. In murine studies, 3 weeks of dietary supplementation of fish oil changed five genes more than 2-fold, and DHA enriched fish oil for approximately 2 months identified 329 and 356 dietary regulated transcripts from liver and hippocampus, respectively. There were no published studies of effects of long-term treatment with EPA and DHA in humans, using genome wide techniques, until recently. Here, we present results of a clinical trial, the Diatrizoic acid OmegAD study, where a product rich in DHA was given to patients with mild to moderate AD. The goal of the OmegAD study was, inter alia, to see if this n-3 preparation would reduce the cognitive deterioration. In the present study of the OmegAD trial, we used global transcriptome profiling to detect new genes responding to DHArich n-3 supplementation in isolated peripheral blood mononuclear cells. Preliminary results from this study has been presented previously. A total of 174 patients completed the OmegAD study. Plasma fatty acid profiles, cognition and behavioural data have been published. A pre-trial power calculation in the whole study, estimated that 200 patients have to be included with a statistical significance level of 0.05 and 80% power to accomplish differences in the measurement of the cognitive function. The estimation of numbers of enrolled patients in our gene expression subgroup by power calculation has not been applicable, due to insufficient knowledge as to variables included in the power calculation for the thousands of genes measured by the microarray technique. Here, we present data on 11 patients, who Octinoxate received the n-3 FAs preparation, and 5 patients, receiving the placebo oil, for 6 months.