Premenstrual dysphoric disorder (PMDD) is a severe form of premenstrual syndrome, afflicting approximately 5% of all women of fertile age. Although selective serotonin re-uptake inhibitors (SSRIs) are considered as the first-line medication in our days, efforts have continuously been made in order to find alternative treatment options. From the 1980s on, a couple of studies drew our attention to the abnormal essential fatty acid levels among women suffering from PMDD. 24 PMDD patients, all having received SSRI treatment before, were treated by the authors for 3 menstrual cycles with 1000 mg QD omega-3-acid ethyl esters. Based on the favourable outcome omega-3-polyunsaturated fatty acid medication augurs well as a treatment option in SSRI- resistant PMDD.