Along with his Pasquino Curio at first published educational writings and books for students in Basel.
In 1551 in the press of Johannes Hervagius he dedicated to Amerbach his richly augmented edition of the Ciceronian lexicon of Marius Nizolius.
He also busied himself as a theological writer.
He contributed a Preface to a Life of Francesco Spiera published by Matteo Gribaldi with Pietro Paolo Vergerio in 1550.
When Castellio in 1554 strongly attacked the conviction of Michael Servetus in a published writing, Curio was suspected of being his co-author by John Calvin and Theodore Beza.

 He gained much attention with his work De Amplitudine Beati Regni Dei (1554), partly presented as a dialogue with Agostino Mainardi.
On account of the incendiary nature of the theological opinions expressed in it, he had it published not in Basel but in Poschiavo, to circumvent the Basel censor.
This work was dedicated to the Polish King Sigismund.
It was rejected by some of Curio's friends, and also by Bullinger.
It was heavily attacked by Vergerio (like Curio a religious exile from Italy, whose Otto Difensioni Curio had published, introduced and defended) and Curio was denounced as an heretic before the Council at Basel: he was able to clear himself largely before the inquisition of the censors.

Through these experiences Curio drew back from theological publication, but he remained in correspondence with the apostles of the Reformation.
In 1554 Sir John Cheke met him in Strasbourg, soon after leaving England in voluntary exile following the accession of Queen Mary, by whom the English reforms were reversed.
Cheke was carrying the seven letters which had passed between him and Stephen Gardiner, Bishop of Winchester, in 1544, when Gardiner had issued a severe prohibition against Cheke's reforms of ancient Greek pronunciation in the University of Cambridge.
Gardiner's letters showed his unpleasant side.

Cheke explained the significance of the letters to Curio and entrusted them to him.
In the following year Curio had them published at Basel without Cheke's knowledge, and they attracted wide interest.
Curio's preface is full of admiration for the teaching of Cheke and Sir Anthony Cooke, and elsewhere extols the learning of Sir Thomas Wroth (all intimates of Edward VI), with whom he dealt in their travels in exile.
On the orders of King Philip Cheke was seized and intimidated into an involuntary formal recantation in 1556.
Curio dedicated his second and later editions of the works of Olympia Fulvia Morata to Queen Elizabeth I of England.
Along with his Pasquino Curio at first published educational writings and books for students in Basel. In 1551 in the press of Johannes Hervagius he dedicated to Amerbach his richly augmented edition of the Ciceronian lexicon of Marius Nizolius. He also busied himself as a theological writer. He contributed a Preface to a Life of Francesco Spiera published by Matteo Gribaldi with Pietro Paolo Vergerio in 1550. When Castellio in 1554 strongly attacked the conviction of Michael Servetus in a published writing, Curio was suspected of being his co-author by John Calvin and Theodore Beza.
 He gained much attention with his work De Amplitudine Beati Regni Dei (1554), partly presented as a dialogue with Agostino Mainardi. On account of the incendiary nature of the theological opinions expressed in it, he had it published not in Basel but in Poschiavo, to circumvent the Basel censor. This work was dedicated to the Polish King Sigismund. It was rejected by some of Curio's friends, and also by Bullinger. It was heavily attacked by Vergerio (like Curio a religious exile from Italy, whose Otto Difensioni Curio had published, introduced and defended) and Curio was denounced as an heretic before the Council at Basel: he was able to clear himself largely before the inquisition of the censors.
Through these experiences Curio drew back from theological publication, but he remained in correspondence with the apostles of the Reformation. In 1554 Sir John Cheke met him in Strasbourg, soon after leaving England in voluntary exile following the accession of Queen Mary, by whom the English reforms were reversed. Cheke was carrying the seven letters which had passed between him and Stephen Gardiner, Bishop of Winchester, in 1544, when Gardiner had issued a severe prohibition against Cheke's reforms of ancient Greek pronunciation in the University of Cambridge. Gardiner's letters showed his unpleasant side.
Cheke explained the significance of the letters to Curio and entrusted them to him. In the following year Curio had them published at Basel without Cheke's knowledge, and they attracted wide interest. Curio's preface is full of admiration for the teaching of Cheke and Sir Anthony Cooke, and elsewhere extols the learning of Sir Thomas Wroth (all intimates of Edward VI), with whom he dealt in their travels in exile. On the orders of King Philip Cheke was seized and intimidated into an involuntary formal recantation in 1556. Curio dedicated his second and later editions of the works of Olympia Fulvia Morata to Queen Elizabeth I of England.
Celio Secondo Curione