The dwindling supply of castrati created a crisis in the opera world in the early 19th century. Castrati had dominated opera seria throughout the 18th century, but by the early 1800s their numbers were in decline. Impresarios and composers explored two voice types as substitutes for the castrato in male leading roles in serious operas: the contralto and the tenor. The study includes data from 242 serious operas that premiered in Italy between 1800 and 1840, noting the casting of the male leading role for each opera. At least 67 roles were created for contraltos as male heroes between 1800 and 1834. More roles were created for tenors in that period (at least 105), but until 1825 there is no clear preference for tenors over contraltos except in Naples. The Neapolitan preference for tenors is most likely due to the influence of Bourbon Kings who sought to bring Enlightenment values to Naples. After the last castrato retired in 1830 and the casting of contraltos as male heroic leads falls out of favor by the mid-1830s, the tenor, aided by a new chest-voice dominant style of singing, becomes the inheritor of the castrato's former role as leading man in serious Italian opera.