Contents: Introduction; Robert Willis, Viollet-le-Duc and the structural approach to Gothic architecture, R. Mark; On the rubber vaults of the Middle Ages and other matters, J. Heyman; The geometrical knowledge of medieval master masons, Lon R. Shelby; Villard de Honnecourt, Reims, and the origin of gothic architectural drawing, R. Branner; The tracing floor of York Minster, J.H. Harvey; Late gothic structural design in 'instructions' of Lorenz Lechler, Lon R. Shelby and R. Mark; The ground plan of Norwich Cathedral and the square root of two, Eric Fernie; The stonework planning of the first Durham master, J.Bony; Archaeology and engineering: the foundations of Amiens Cathedral, S. Bonde, C. Maines, and R. Mark; The collapse of 1284 at Beauvais Cathedral, S. Murray; Beauvais Cathedral, J. Heyman; The structural behaviour of medieval ribbed vaulting, K.D. Alexander, R. Mark and J.F. Abel; Fan vaulting, Walter C.Leedy Jr.; Ars mecanica: gothic structure in Italy, Elizabeth B. Smith; Brunelleschi's dome of S. Maria del Fiore and some related structures, R. Mainstone; A comment on the function of the upper flying buttress in French gothic architecture, J. F. Fitchen; The high roofs of the east end of Lincoln Cathedral, N.D.J. Foot, C.D. Litton and W.G. Simpson; Viollet-le-Duc and the fleche of Notre-Dame de Paris: gothic carpentry of the 13th and 19th centuries, L. Courtenay; Building the tower and spire of Salisbury Cathedral, Tim Tatton-Brown; Index.