When accused by Sulla (to whom he had been quaestor in 81 BC) of having squandered the public money, he refused to render any account, but insolently held out the calf of his leg (sura), on which part of the person boys were punished when they made mistakes in playing ball, akin to inviting a slap on the wrist.
When Catiline left Rome after Cicero's second speech In Catilinam, Lentulus took his place as chief of the conspirators in the city.
In conjunction with Gaius Cornelius Cethegus, he undertook to murder Cicero and set fire to Rome, but the plot failed owing to his timidity and indiscretion.
On learning that ambassadors from the Allobroges were in Rome bearing a complaint against their oppression by Roman provincial governors, Lentulus made overtures to them with the object of obtaining armed assistance.
He was put to death in the Tullianum on 5 December 63 BC, along with other senatorial supporters of Catiline.