Abstract: An organ perfusion system comprises: a perfusion fluid circuit (16) arranged to circulate perfusion fluid through the organ; a surrogate organ (126) arranged to be connected into the circuit in place of the organ so that the circuit can circulate fluid through the surrogate organ; and organ sensing means arranged to distinguish between the presence of the organ in the circuit and the presence of the surrogate organ in the circuit. The sensing means may comprise one or more pressure sensors (136, 137, 138), or a flow meter (125). Further aspects relate to adjusting the content of at least one component, such as oxygen or a nutrient, in the perfusion fluid. Bubble detection means (113), and means (74) to measure the amount of fluid secreted by or leaked from the organ, may also be provided.