Lancelotto Avellino studied canon and civil law at Naples, was ordained priest in 1545, and served for years as ecclesiastical lawyer at the Curia of Naples. After a serious moral crisis at a court case — where he had told a tactical untruth and was struck open at his next reading of Scripture by the verse 'The mouth that lies destroys the soul' — he abandoned the law in 1556 to enter the Theatines (the order founded by Cajetan, then under twenty years old) at the Roman house at San Paolo Maggiore in Naples. He took the religious name Andrea.
He worked for over fifty years as Theatine preacher, confessor, and superior — at Naples, Milan, and Piacenza. He was the personal friend and frequent correspondent of Charles Borromeo (who used him as a model of pastoral reform in the Theatine houses of Lombardy), of Charles's nephew Federico Borromeo, and of the future Pope Paul V. He survived an assassination attempt by hired thugs of a corrupt clergyman in 1576.
He died at the altar at San Paolo Maggiore on November 10, 1608, at eighty-seven — stricken with a sudden seizure as he began the words of the Introit of the Mass. The episode — the dying priest collapsing at the altar at the start of the Holy Sacrifice — became the basis of his patronage against sudden death, particularly invoked by Italian and Spanish Catholics for the grace of a holy death. Canonized 1712.