There are several risk factors involved in the pathogenesis of breast cancer. The role of non-steroidal anti-inflammatory drugs (NSAIDs) in the development of breast cancer has not been fully clarified. In order to investigate the impact of NSAIDs ingestion on prognostic factors of breast cancer we studied a total of 341 women with invasive carcinoma of the breast who presented between March and September 1993 to the Breast Cancer Clinic of the H. Lee Moffitt Cancer Center in Tampa, Florida. We noted that ingestion of NSAIDs was inversely associated with the size of the primary tumor, the lymph node status, and the number of involved axillary nodes. ingestion of NSAIDs may impact favorably on factors that determine the prognosis and clinical outcome of women with breast cancer.