Relatively little critical attention has been paid to the conventions that govern the ways that Spanish Golden Age plays begin. This study defines a set of conventions for these play beginnings and offers some theoretical precepts that helped to shape the conventions. After reviewing the comments on play openings found in contemporary theoretical treatises of the period, this study offers some observations on play openings for Lope de Vega and Tirso de Molina. Factors considered include the number of characters onstage, the use of vertical space, sound effects, machinery and other special effects, and beginnings of (apparent) harmony vs. beginnings of crisis. The play openings of Calderón de la Barca are then studied at some length. Finally, this article seeks to show how Golden Age play beginnings were at least in part shaped by external considerations of representation and circumstance, such as the theatrical troupe for which a given play was composed. (JTC)