The direction of translocation of C14 following the assimilation of C14O2 by single leaves or shoot tips of the Muscat of Alexandria grapevine was determined by using radioautographic techniques. The first assimilate exported by the treated leaf was to the shoot tip. When the treated leaf was separated from the oldest importing leaf on the shoot tip by two or three other exporting leaves, the assimilate from the leaf was translocated both to the shoot tip and to the parent vine. With further shoot growth the basipetal movement predominated until translocation from a treated leaf below the shoot tip was completely reversed and was basipetal only. Translocation from leaves below the cluster was partially reversed again when fruit development started. Assimilate from these leaves was translocated both to the fruit cluster and parent vine. After the rate of shoot elongation decreased sharply, radiocarbon moved from the shoot tip in a basipetal direction. The young inflorescence had small power as a sink compared to the shoot tip and the parent vine, and was unable to influence the direction of translocation. From 10 to 14 days before bioom until fruit set the cluster was a weak sink. Axillary buds, tendrils, xylem, parenchyma, and pith were found normally to be weak sinks relative to the developing fruit cluster and unable to influence the longitudinal direction of translocation. Axillary shoots behaved as young leaves until 1 or 2 of their leaves were mature. Then no assimilate moved into them from the main shoot. Shoot tips and parent vines were more powerful sinks than the cluster during flower development but not during fruit set. Girdling and topping thus affect fruit set because they divert more assimilates into the cluster just prior to fruit set.