It is known the importance of mercantile corporations in the increment of medieval naval commerce.However, the analysis of the Merchants University of Bilbao, the largest Cantabrian Batteries - Chargers port of pre-industrial Castile, has been relegated due to lack of documentation.But, thanks to the discovery of new sources, very abundant and of great documentary wealth, I Twin Sleigh Storage Bed present this study on the structure of the mercantile guild and its activity of port management before its constitution in a Consulate of the sea, instituted by the Crown in 1511.