This essay focuses on the manuscript and printed sources assessed by Aquiles Estaço (1527-1581) for his epigraphic compilation in Codex B. 104 of the Biblioteca Vallicelliana. The case of the Portuguese humanist is quite illustrative of the antiquarian network that flourished in 16th century Rome, since Estaço's interests were the same as most European scholars of the period. The interaction between humanists, the exchange of ideas and information can be seen through his papers and this codex, which remains unedited in the Biblioteca Vallicelliana, offers a direct testimony. Key words: Aquiles Estaço, Roman epigraphy, textual transmission, 16th century antiquarians.