The present volume contains Enea Silvio Piccolomini’s 104 personal letters from the years 1455 and 1456, i.e., his last half year at the Imperial Court in Austria and the year and a half when he was back in Italy before he was appointed a cardinal. Of these letters, 45 have never been published in print; 11 have only been published in incunabula editions and later in the Opera Omnia edition from 1551; and 48 have been published in modern critical editions (in RTA).