It has shown recently that Evening Primrose Oil (Efamol) produces a significant clinical improvement in atopic eczema. Efamol contains gamma-linolenic acid which is a precursor to PGE1 a more consistent bronchodilator than PGE2. We have conducted a double blind placebo controlled study in atopic asthmatics given Efamol for an eight week period looking at the control of asthma, including histamine challenge tests. We have found no effect on the asthma or challenge tests although Efamol produced an alteration in fatty acid profile. The patients showed an abnormal fatty acid profile. We speculate that such fatty acid abnormalities could be important in the aetiology of asthma.