This document presents the development trouser role. The first part is concentrated in the seventeenth century when the use of castrati was the main business in church music. Later in the same chapter is presented the development of women in opera, which so far was not a common practice, and how and why they dominate the opera after the castrati were not an accepted practice anymore. The following chapters contain demonstrations of trouser role’s types. Each chapter is based in one role of an opera from a different period of history. From Gluck’s Orfeo ed Euridice to Strauss’ Der Rosenkavalier, the pants role is exemplified from a different point of view according to their importance in opera.