Arachidonic acid (ARA) is one the two main polyunsaturated fatty acids (PUFAs) in the brain, especially in neuronal cells, and can be a target in the fight against the major public health concern represented by Alzheimer’s disease (AD) and related disorders in high- as well as in low-income countries where elders constitute a growing part of the population. This compilation includes topics such as the use of arachidonic acid to prevent Alzheimer’s disease; the dietary effects and sources of ARA; the effect of ARA on key oncogenic pathways in prostate cancer; and the effects of adipokines on prostaglandin E2 production by rheumatoid synovial fibroblasts.