There is always an interval between the first symptoms, time to diagnosis and start of treatment in women with symptomatic breast cancer. Delay may be due to the patient, her general practitioner or a false negative diagnosis in hospital. A systematic overview showed that delays of 3-6 months were clearly associated with increased tumour size, advance in disease stage and poorer long-term prognosis. Nevertheless, controversy persists regarding the impact of delay on survival. The conflicting results may be due to a difference in sample characteristics, differences in the delay interval studied or variations in the definition of delay. A major drawback of many studies was that the potential confounding effect of lead-time bias was not taken into account. One of the largest single institution studies, designed to control for the lead-time bias, confirmed that survival measured from both date of diagnosis and onset of patient's symptoms was worse in women with delays of >12 weeks. Within individual stages, longer delays had no adverse impact on survival. It is important to identify groups of patients at high risk of delay so that strategies can be developed and effectively targeted.