Being a handsome youth, his chastity was often exposed to danger from female admirers, and to escape their importuning he took ecclesiastical tonsure.

Certain wicked men who were accustomed to having clandestine meetings with the nuns became exasperated at the saint's interference, and one night he was assaulted and severely wounded.

Here, however, he resolved to devote himself entirely to God and he entered the Order of Theatines, which had only recently been founded by Gaetano dei Conti di Thiene.

[3] After completing his novitiate, he obtained permission to visit the tombs of the Apostles and the Martyrs at Rome, and, upon his return, was made master of novices.

His zeal for strict religious discipline and for the purity of the clergy, as well as his deep humility and sincere piety, induced the General of his Order to entrust him with the foundation of two new Theatine houses, one at Milan and the other at Piacenza.

As superior of some of these new foundations, he was so successful in converting sinners and heretics by his prudence in the direction of souls and by his eloquent preaching that numerous disciples thronged around him, eager to be under his spiritual guidance.

Avellino collaborated with Paolo Burali d'Arezzo] in implementing the reforms of the Council of Trent in the Diocese of Piacenza.