GIROLAMO CARDINAL COLONNA DI SCIARRA (1708-1763), son of Francesco Colonna (4th Prince of Carbognano) and Vittoria Salviati, belonged to the celebrated Roman family of the Colonna, only one of whose members, Martin V, ever became pope. He became a Cardinal deacon on September 9, 1743, delaying his reception of minor orders until 1746; he became Bishop of Sant' Agata dei Goti; he was appointed archpriest of S. Maria Maggiore. He was made Vice-Chancellor of the Holy Roman Church in 1753, and was appointed Camerlengo of the Holy Roman Church on September 20, 1756, a post he held until his death on January 18, 1763. He was Grand Prior in Rome of the Order of St. John of Jerusalem.

The Dean of the Sacred College of Cardinals was Raniero Cardinal d' Elci. He had been Nuncio to the French Court in the 1730's.

The Governor of the Conclave was the Prefect of the Apostolic Palaces, Monsignor Marcantonio Colonna (born in Rome August 16, 1724; died there December 4,1793), a member of the Roman nobility, A Neapolitan patrician, and a Venetian patrician. He was the son of Principe Don Fabrizio Colonna, 10th Prince and Duke of Paliano, and Caterina Salviati, daughter of the third Duke of Giuliano. He became a Cardinal in 1759, and was assigned the titulus of Santa Maria in Aquiria (which he exchanged for Santa Maria della Pace in 1762, and San Lorenzo in Lucina in 1764). Ordained in 1761, he was promoted titular Archbishop of Corinth in 1762, and became Vicar General of the city of Rome. He was made Archpriest of Santa Maria Maggiore (the Liberian Basilica) in 1775. In 1784 he was further promoted to the title of Cardinal Bishop of Palestrina.

	AE SEDE | VACANTE Shield with the Coat of Arms of Marcantonio Colonna, Prefect of the Sacred Apostolic Palaces and Governor of the Conclave, surmounted by a clerical hat with six tassels on each side...
	MARCVS•ANTON COLVMNA S•PAL:APOST: PRAEFECTVS ET•CONCLAVIS GVBERNATOR MDCCLVIII Inscription: "Marcus Antonius Colonna, Prefect of the Sacred Apostolic Palaces and Governor of the Conclave, 1758.".

Pope Benedict XIV died on May 3, 1758, aged eighty-three, after a long period of suffering from gout (Montor, 109).

On May 15, twenty-seven of the fifty-five cardinals entered conclave. Five cardinals who were in Rome that day did not enter conclave due to illness. Ten cardinals did not participate at all. Cardinal de' Bardi had originally joined the conclave, but he left on June 24. There were, therefore, fourty-four electors in the later stages of the conclave. Thirty votes were needed for a canonical election.

Cardinal Carlo Corsini (nephew of Clement XII), Cardinal Joaquin Portocarrero Mendoza (Cardinal Bishop of Sabina), and Cardinal Domenico Orsini d' Aragona (nephew of Benedict XIII) undertook to promote the candidacy of Cardinal Carlo Alberto Cavalchini (the Prefect of the Sacred Congregation of Bishops and Regulars). On May 29, Cardinal Franz Konrad de Roth (Bishop of Konstanz) entered conclave, bearing the instructions of the Imperial Court in Vienna. The results of the balloting on June 19 showed that Cardinal Cavalchini had obtained 21 votes. This made his election a serious possibility. On the 21st, his total had risen to twenty-six (Wahrmund 229; Montor says twenty-three). On that same evening, Cardinal de Luynes, acting on instructions from the French government, presented to Cardinal d'Elci, the Dean of the Sacred College, the veto (exclusiva) against Cardinal Cavalchini; it is said that the reason was that Cavalchini was favorable to the Jesuits and had voted for the canonization of Robert Cardinal Bellarmine, SJ (Ravignan, 30).

It was apparently Cardinal de Roth and some of his associates who decided to put forth the name of Cardinal Rezzonico. In the balloting on July 4 he received 22 votes. On the 6th, he received thirty-one votes, which brought him canonical election.

On July 6, the Venetian Cardinal Carlo della Torre Rezzonico, Bishop of Padua, was elected. He was crowned in St. Peter's on July 16, and he took solemn possession of the Lateran Basilica on November 13.