The relationship is clarified between the form of choux pastry when baking, and the expansion and cavity formation in choux pastry prepared at different preheating temperatures.The preheating temperature was varied from a level at which the dough did not gelatinize to a higher level. Experimental results show that the expansion and cavity formation in choux pastry depended on its form for baking despite its degree of gelatinization or viscosity. Choux pastry samples free on a baking sheet and preheated up to 98℃ could expand with a single cavity during subsequent baking at more than80℃, but could not expand when preheated up to 70℃. Although choux pastry samples placed in a baking cup and preheated up to 70℃ could expand during subsequent baking. DSC measurements showed that the dough had not sufficiently gelatinized when preheated to this temperature. Despite adequate viscosity when preheating the dough up to 98℃, expansion and cavity formation were insufficient with some sizes of baking cup. The preheating temperature was not critical for good expansion and cavity formation to be obtained with the ratio (height/diameter) of dough more than 0.14.