In his various works Jérôme makes a large use of secular poetic quotations. Many scholars have already searched new ones or observed those who are recurring. Lots of studies concerning classical quotations by Jérôme are connected too to the vow of the famous dream of the Letter 22, 30. The present paper aims at showing how Jérôme makes use of such quotations in his Letters and what a rhetorical or dialectical place these take in his writing. The Letter 60, to Heliodore with his eight secular poetic quotations gives a good example on the subject. This is the reason why it allows suggesting a classification of various uses of these quotations by Jérôme in his Letters. This classification may be used, we hope so, for all kind of secular quotations by Fathers of the Church.