Premenstrual syndrome is a common disorder troubling many women during their reproductive years. The Chinese have been using herbal medicines to treat menstrual cycle related symptoms for centuries. Traditional Chinese medicine provides the aetiology and pathogenesis of the symptoms of this disorder by applying Pattern Identification to diagnose the signs and symptoms of individual patients and to design individualised treatments which seek to address the entire pattern/s of disharmony. It follows that PMS, which has many symptoms and an idiosyncratic nature, is precisely an area for which Chinese medicine is most suitable. The aim of this study is to scientifically evaluate the effectiveness of Chinese herbal medicine on Australian women for the treatment of PMS within the theoretical frame-work of TCM. A double-blind randomized placebo-controlled crossover clinical trial was conducted by a qualified Chinese herbal practitioner and pharmacist. Following two months confirmatory assessment, sixty-one subjects were assigned randomly into two groups within different TCM patterns of Liver Qi Stagnation, Liver and Kidney Yin Deficiency, Liver and Spleen Disharmony and Heart and Spleen Deficiency. Herbal medicine (n=31) and placebo (n=30) were provided sequentially for a period of three months. There were significant differences (p < .01) in scores after three months of treatment between Chinese herbal medicine and placebo in premenstrual physical and psychological symptoms, depression, anxiety and anger, but with no difference in perceived stress (p > .05). There were highly significant reductions (p< .001) in all assessments in both groups except that a significant result (p < .05) was recorded on perceived