Asthma is a chronic inflammatory disease of the airways mediated, at least in part, by leukotrienes and other lipid mediators. Experimental studies have shown that lipid extract of New Zealand green-lipped mussel, Perna canaliculus, is effective in inhibiting 5'-lipoxygenase and cyclo-oxygenase pathways responsible for production of eicosanoids, including leukotrienes and prostaglandins. The aim of this study was to assess its effect on symptoms, peak expiratory flow (PEF) and hydrogen peroxide (H2O2) in expired breath condensate as a marker of airway inflammation in patients with steroid-naïve atopic asthma in a double-blind randomised, placebo-controlled clinical trial. Forty six patients with atopic asthma received two capsules of lipid extract (Lyprinol) or placebo b.i.d for 8 weeks. Each capsule of lipid extract contained 50 mg omega-3 polyunsaturated fatty acids and 100 mg olive oil, whereas placebo capsules contained only 150 mg olive oil. There was a significant decrease in daytime wheeze, the concentration of exhaled H2O2 and an increase in morning PEF in the lipid extract group compared to the placebo group. There were no significant side-effects. The authors conclude that lipid extract of New Zealand green-lipped mussel may have some beneficial effect in patients with atopic asthma.