Contains handwritten letters on paper, many of which are partially or entirely in code. The letters are written to Pope Gregory XIV and his brother, Paolo Sfondrati, and relate to the family's political and Catholic Church relationships in Italy and Spain.

Collection includes letters, promissory notes, and other handwritten documents relative to matters between the Sfondrati family and political leaders in the region. Many of the items relate to family financial matters. Materials date from between 1531 and 1788.

Contains depositions, legal opinions, letters, and other materials from the Sfondrati family. Much of the materials deal with the inheritance of lands from Isabella di Capua, of the Cybo-Malaspina family of Massa.

Contains letters to and from members of the Sfondrati family. These materials relate to personal as well as many political and Church matters in Italy and Europe. One of the items is from King Henry IV of France.

Contains handwritten documents on parchment related to members of the Sfondrati family. These materials concern personal as well as political and Church matters in Cremona and Mantua, Italy, and other parts of the region.

Contains legal documents, land records, and family papers related to the Sfondrati and associated families in northern Italy. The papers primarily deal with the heraldry and land holdings of the family in the region. Notes and other materials by later researchers in the collection are also included. The materials date from between 1494 and approximately 1900.

Contains handwritten and printed items relating to the administration of the fiefdom of Guadalcanal. Includes information on the assignment of the area to Ercole Sfondrati, as well as its later administration. The materials also document the conflict between Sfondrati and Gaspar Alfonso Perez de Guzman over its control. Documents date from between 1599 and 1659.