Eleven cardinals were absent: Seven of them were appointed by Gregory XIII and four by Sixtus V. As during the previous conclave there were three large factions:[3] There were two small groups practising nepotism.

The Cardinals who were considered as papabile were Serbelloni, Marchntonio Colonna, Gallio, Paleotto, Madruzzo, Santori, Facchinetti, Sfondrati, Valier, Lauro, della Rovere.

[4] In the context of this conclave, the Prophecy of the Popes was forged, probably in order to support Cardinal Girolamo Simoncelli's bid for the papacy.

[5][6] On 6 October, even before the conclave had started, the Spanish ambassador Olivares gave the Cardinals the official recommendations of King Philip II.

A few days later, Camerlengo Caetani joined them after his return from France, and on 13 October Cardinal Andreas von Österreich arrived.

Objections against Madruzzo included his close ties with the king of Spain, his poor state of health (he was impaired by gout), and even his origin (his mother was German).

[11] After the rejection of Madruzzo, Cardinal Montalto offered the Spanish faction five names — Aldobrandini, Lauro, Valiero, Salviati and Medici — and asked them to pick one.

[12] At the end of November, the majority of cardinals gradually came to the conclusion that no matter how outrageous the interference of Philip II, without the support of his followers there was no chance to elect a Pope, so it would be better to choose someone from his list.

[13] On the morning of 5 December 1590, after nearly two months' conclave, 55-year-old Cardinal Niccolo Sfondrati, Bishop of Cremona, was elected Pope, and chose the name Gregory XIV.