IgA nephropathy (IgAN) is now recognized as the most common primary glomerulonephritis worldwide. Although the clinical course is variable, many patients develop slowly progressive renal disease, culminating in end-stage renal disease 10-20 years after diagnosis. Some recent randomized clinical trials have suggested that dietary fish oil supplementation may be a relatively safe long-term therapeutic option for preventing the development of progressive renal disease in patients with IgAN. However, other studies have failed to demonstrate a protective effect of dietary fish oil supplementation in treatment of IgAN. Although in vitro studies have provided a theoretical basis for the use of dietary fish oil supplementation, potential mechanisms underlying the protective effect of fish oil have not been well defined. In this overview, recent clinical and experimental data providing a basis for the use of dietary fish oil supplementation in treatment of IgAN and other progressive renal diseases are reviewed.