When (14)C-sugar and THO were simultaneously introduced through a cut side vein or flap of a squash leaf (Cucurbita melopepo, Bailey cv. torticollis) concurrent translocation of (14)C-sugars, T-photosynthates and THO with parallel, almost flat, gradients was observed in the petiole for periods of 1 to 3 hr. Parallel translocation gradients were not observed when (14)C was introduced as (14)CO(2) and T by painting a leaf with THO. Autoradiography of frozen sections to locate the tissues in which THO was moving was unsuccessful. Steam-girdling blocked the movement of (14)C and T when (14)C-glucose and THO were introduced simultaneously by the flap-feeding technique. If THO moved as liquid water in the phloem along with the (14)C-sugars, as blockage by steam girdling suggests, then solution flow of sugar cannot be excluded as a mechanism of translocation.