Congestion, or fluid overload, is a classic clinical feature of patients presenting with heart failure patients, and its presence is associated with adverse outcome. However, congestion is not always clinically evident, and more objective measures of congestion than simple clinical examination may be helpful. Although diuretics are the mainstay of treatment for congestion, no randomised trials have shown the effects of diuretics on mortality in chronic heart failure patients. Furthermore, appropriate titration of diuretics in this population is unclear. Research is required to determine whether a robust method of detecting — and then treating — subclinical congestion improves outcomes.