Endoscopy has revolutionised our management of many gastrointestinal disorders over the past 30 years. We are increasingly able to diagnose gastrointestinal (GI) tumors at an early stage, and endoscopic therapy has made a difference to the outcome of GI haemorrhage. We still rely on surgery for cure of cancer but as diagnostic techniques improve the goal of minimally invasive diagnosis and therapy appears ever more attainable. As populations get older, it is also increasingly desirable. Laser light can be used for both diagnosis and therapy in the gut. This article reviews the value of lasers in these areas.