By washing out 14C-labelled assimilates from the free space of stem segments of Vicia faba L., considerably more label could be removed from a stem parasitised by Cuscuta species than from a normal one. This could mean that the moving of assimilates from the host phloem to the parasite at least partly occurs through the apoplast. The assumed unloading of the host phloem is apparently under metabolic control since it appeared to be inhibited at 0°C and after addition of dinitrophenol.