Grapevines (Vitis vinifera L., cultivars Muscat Gordo Blanco and Sultana) were grown in controlled-environment growth cabinets. At intervals, up to 13 weeks after bud burst, shoots were harvested, and both the number and fresh weight of leaf primordia, in buds at certain nodes, were measured. Bud development, in terms of leaf primordia, was depressed, with reduction in both light intensity and temperature. This parallels effects on initiation of bunch primordia. Bud development outdoors was similar to that in growth cabinets under the best conditions. At the time a node was separating macroscopically below the shoot apex, its subtended bud consisted of an apical dome and two leaf primordia. It was known that temperature had its greatest effect on subsequent fruitfulness of a bud at this stage. About 3 weeks after the shoot apex had grown away from a node, the bud situated at that node consisted of an apical dome and approximately six leaf primordia. It is at this stage that the fruitfulness of a bud is known to be no longer susceptible to temperature. It is concluded that temperature influences fruitfulness of grapevine buds by effects on tissues which exist prior to, and which are subsequently situated basal to, a fruit primordium.