The lifetime prevalence of asthma in California is nearly 20%, and better therapies are needed to manage this common chronic disease. Fish oils containing omega-3 fatty acids are considered a potential therapy for asthma and other inflammatory diseases. Fish oil inhibits the production of arachidonic acid 5-lipoxygenase (ALOX5), an enzyme that exacerbates the lung inflammation that causes asthma. We discuss the genetics of asthma and our preliminary results using a strategy to identify the subgroup of patients who may respond well to treatment with fish oil. These findings, and others, suggest that certain gene polymorphisms of the ALOX5 gene predispose patients to the increased production of inflammatory leukotrienes. Our clinical trials will test the hypothesis that patients with moderate to severe asthma, and with specific high-risk ALOX5 gene sequence variations, will have fewer asthma symptoms when treated with fish oil. The strategy is to decrease the total burden of leukotriene production by supplementing with omega-3 polyunsaturated fatty acids. These studies will also help determine whether genotyping or metabolic profiling (for example, with exhaled breath condensate) can help establish "personalized medicine" for asthma.