The first known bishop, Alexander, was consecrated by John Chrysostom about 400.

The diocese was founded by the year 1155, when the first known bishop, Bishop Laurence, appears on record.

Its first known bishop is Mauritius (680); other bishops were:

The first known bishop of Asti was Pastor in 451.

The first known bishop was Amandus (about 500).

The first known bishop was Candidus (465); among his successors were:

The first known bishop of the city was a certain Zenon in the late 4th or early 5th century, mentioned by Sozomenus.

Le Quien gives a list of the known bishops:

The first known bishop is Desiderius, mentioned in 1082, but he is known to have had predecessors.

Its first known bishop attended a council at Salona in 530.