Using the facultative root hemiparasite Rhinanthus minor L. and Hordeum vulgare L. as a host, the flows, depositions and metabolism of zeatin-type cytokinins [zeatin (Z), zeatin riboside (ZR), zeatin nucleotide (ZN)] within the host, the parasite and between host and parasite have been studied during the period 41–54 d after planting (i.e. ~30–43 d after successful attachment of the parasite to the host). Parasitism decreased the synthesis of Z in the root (by 57%) and decreased xylem flows (by 56%) and metabolism (by 71%) in leaf laminae. However, phloem flows of Z were increased by 3-fold in the host barley. The deposition of Z in the roots of Rhinanthus and the flows in xylem and phloem were increased by 20, 12, 29-fold, respectively, after successfully attaching to the host barley. However, net biosynthesis of Z in Rhinanthus roots decreased by 35% after attachment. This indicates that a large portion (70%) of xylem flow of Z in attached Rhinanthus was extracted from the host. In singly growing Rhinanthus plants, the balance of Z deposition in the shoot was negative (i.e. Z was metabolised and exported back to root in the phloem). Xylem flows and deposition of ZR and ZN showed comparable quantitative changes after attachment. A significant deposition of Z, ZR and ZN was detected in the haustoria of the Rhinanthus / barley association. The possible physiological functions of the large quantities of Z and ZR and ZN derived from the host barley, for the improved leaf development and the stomatal reactions of the parasitising Rhinanthus are discussed.