The current invention provides a new organ preservation solution, suitable for machine perfusion, for maintaining viability of organs, parts of organs and tissues. This solution has been designed to overcome a number of problems associated with hypothermic machine perfusion of donor organs, in particular organs obtained from non-heart-beating donors . The solution prevents or minimizes the adverse affects caused by ischemia, hypoxia, energy and nutrient depletion, acidification, hypothermia and reperfusion injury, by supplying increased concentrations and an optimized balance of amino acids, vitamins, anti-oxidants, high molecular weight additives and enhanced buffering capacity.