Patients who have limited options might wish to access experimental treatments despite uncertainties about safety and efficacy and the often substantial financial costs involved. Healthcare professionals have important responsibilities to support patients to make informed decisions about treatments for which evidence is limited. Particular issues arise when making decisions about the use of experimental treatments in children and others without capacity to decide for themselves. A key challenge is balancing the interests of patients in accessing experimental treatments with ensuring protection from harm, particularly when treatments are offered outside the UK regulatory framework. Further questions are raised about how best to capture the knowledge gained from the use of experimental treatments, and ensure that their offer does not undermine research that might benefit patients in the future.