The aim of this study was to identify the factors influencing entry of women with invasive breast cancer into clinical trials in Scotland. Women diagnosed during 1987 and 1993 were identified from cancer registry data records and their case notes reviewed. Entry into clinical trials was recorded, along with clinical and demographic data for 4688 patients. In 1987, the proportion of women entering clinical trials was 12.3% and, allowing for shorter follow-up, this appeared unchanged in 1993. Patients seen by surgeons with a high case load and those referred to an oncologist were approximately seven times and three times, respectively, more likely to enter a clinical trial (P < 0.0001). The area of Scotland (Health Board) where the woman was first treated also influenced study entry (P < 0.0001), whereas social deprivation had no effect (P = 0.93). Older women, especially those over 80 years of age, were less likely to enter studies (P = 0.05). Extending the management of patients by specialist multidisciplinary teams should increase recruitment into clinical trials and help to identify better treatments for women with breast cancer.