More than a half of the pages from any classic issue of Proa Magazine are dedicated to advertising. Although it is a vital content for Proa, it has been traditionally treated as secondary material. Through a graphic study and an inventory, this research provides data about which design technics were used for the elaboration of the adverts, which were its references, what kind of companies advertised and what commitment did they have with the Colombian architectural associations of that time. This study shows the importance of advertising in Proa as a primary source of documentation, and tests research tools that could be applied to the analysis of advertising in architecture magazines outside the Colombian context.