Cornelis Engebrechtsz. (ca. 1462-1527) was the first major Leiden painter to whom works can be attributed with certainty. These include a Triptych with the Lamentation, dated ca. 1508 and a Triptych with the Crucifixion, probably a decade later, both of which were made for the Marienpoel Convent near Leiden, and which are now in the Museum De Lakenhal in Leiden. These Leiden altarpieces display the influence of the dynamic mannered style and palette of the Antwerp Mannerists, including rather splendid gold brocades. On the basis of the documented works not more as dozen paintings and some fragments can be attributed to the Master himself but many more can be connected to his workshop. This makes it likely that he had a large workshop specialising in devotional works. Engebrechtsz.'s pupils include his three sons, Pieter Cornelisz named Kunst (c. 1490-1560/61), Cornelis Cornelisz named Kunst (1493-1546) and Lucas Cornelisz named De Cock (1495-before 1552); in addition, Engebrechtsz. most likely was the second teacher, around 1508, of Lucas van Leyden (1489 or 1494-1533) and from ca. 1515, he trained also Aertgen Claesz., better known as Aertgen van Leyden (ca. 1498-ca. 1564). Although his pupils, and above all his three sons, must have played an important role in the shop, it has so far proved difficult to associate one or more of them with specific paintings. The question of attributions is further complicated by the large group of paintings formerly attributed to the Antwerp master Jan (Wellensz.) de Cock (ca. 1470-1521) and now usually attributed to the sons of Engelbrechtsz's or more generally to his workshop. Using as a point of departure the dissertation by Walter Gibson on Engebrechtsz. and his workshop, published in 1977, the present volume also draws upon the subsequent technical investigations of many of the paintings. The spectacular underdrawing of the paintings revealed with infrared reflectography has given better insights in the working methods of the artist and his workshop, and it is now possible to characterize more clearly Engebrechtsz.'s stylistic development, his workshop production, and the different hands involved. The group paintings formerly attributed to Jan de Cock have been more plausibly connected with a Master J. Kock, who was probably trained in landscape painting in Antwerp, and probably moved to Leiden in the 1520's, through it remains difficult to connect him with the Engebrechtsz. workshop. A final chapter of the book is devoted to his works. The book concludes with a catalogue of about 90 paintings, connected with both workshops, summarizing technical material presented in the exhibition-catalogue Lucas van Leyden en de renaissance (spring 2011, Leiden) and updated by the results of the investigations conducted during this exhibition.