This is the first volume of a new English-language edition of the monumental compendium by Manoel Jose da Costa Felgueiras Gaio, "Nobiliario de Familias de Portugal," composed of 33 books and encompassing more than 500 families. In this volume, each Abreu family branch is traced for as many as fifteen or sixteen generations, in lines extending along five centuries. Internal cross-references link different branches and different families. Use of charts and a complete name index at the back of the volume clarify relationships between families.