Early detection of pre-cancerous lesions may allow for more successful treatment - however this raises questions regarding the psychosocial and economic burden of diagnosing disease which is asymptomatic and may never progress to cancer in the lifetime of the individual. In this lecture I will use one disease example which exemplifies many of the controversies and opportunities associated with the early detection of cancer. Barrett's oesophagus is the precursor lesion to cancer of the lower oesophagus: Barrett's oesophagus is estimated to affect 1.6% of the population and 2.3% of those with heartburn symptoms, however the majority of patients are undiagnosed. The cancer conversion rate is 0.5-1% per annum and once a cancer has progressed to a symptomatic stage the five year survival is an abysmal 13%. This lecture will discuss the current state of the Barrett's oesophagus field and the lessons that are germane to making clinical progress in other preinvasive lesions.