There is considerable evidence to suggest that prostaglandins play an important role in the development and growth of cancer. The enzyme cyclo-oxygenase (COX) catalyses the conversion of arachidonic acid to prostaglandins. In recent years, there has been interest in a possible role for COX inhibitors in the prevention and treatment of malignancy. Cyclo-oxygenase-2 (COX-2) is overexpressed in several epithelial tumours, including breast cancer. Preclinical evidence favours an antitumour role for COX inhibitors in breast cancer. However, the epidemiological evidence for an association is conflicting. Trials are being conducted to study the use of COX inhibitors alone and in combination with other agents in the chemoprevention of breast cancer, and in the neoadjuvant, adjuvant, and metastatic treatment settings. In evaluating the potential use of these agents particularly in cancer chemoprophylaxis, the safety profile is as important as their efficacy. Concern over the cardiovascular safety of both selective and nonselective COX-inhibitors has recently been highlighted. Breast cancer is the most common malignancy in women in industrialised nations and the second leading cause of female cancer-related mortality. Approximately 40 000 women develop breast cancer in the UK each year. The incidence of breast cancer has increased by two-thirds over the last 15 years. Mortality rates though have fallen by one-third, and this is likely to be due to earlier detection of breast cancer because of screening, and the increased use of adjuvant therapies. In recent times, the prospect of further improvements in mortality rates has grown with hope provided by new chemotherapy agents and monoclonal antibody therapy directed at cell surface molecules. But can we do even better for women with breast cancer using cheap and simple treatments that are in current use?Nonsteroidal anti-inflammatory drugs (NSAIDs) are a group of widely available, inexpensive medicines. The analgesic, antiinflammatory, antipyretic and antithrombotic effects of salicylate in willow bark and other plant extracts were recognised in ancient Egypt and Greece. These properties have been extensively exploited in numerous fields of clinical medicine since the 19th century, and in cancer patients primarily for analgesia.