This important collection features materials related to the Danish artist Asger Jorn, the French intellectual Guy Debord, and various other figures associated with the Situationist International (SI), a historic avant-garde group revered for its cultural and theoretical production from 1957 to 1972. The SI served as a critical reference for the May 1968 student demonstrations that began in Paris and spread across Europe and elsewhere, with passages from Debord and other members' publications enlisted as slogans and points for debate and action.

Widely regarded as the last of the artistic avant-gardes, the SI was officially founded in Cosio d'Arroscia, Italy, in 1957 through the merging of three groups: the Letterist International, a breakaway faction of the Lettriste group founded by Isidore Isou; the International Movement for an Imaginist Bauhaus, which arose from the short-lived CoBrA group (its name derived from the initials of the members' home cities: Copenhagen, Brussels, and Amsterdam); and the London Psychogeographical Association. The SI published a journal, Internationale Situationniste (1958–1969), that served as the group's organ and expounded its central concepts. In the initial period from 1957 to 1962, these concepts were oriented more toward psychogeography and the dérive (drifting), which involved creating situations (hence the group's name) in urban environments that encouraged creativity and a critical attitude toward everyday life. Another core idea was détournement (rerouting or hijacking), which involved the creative reuse of textual or audiovisual material—marking a precedent to modern-day appropriation or sampling—and which became a fundamental part of the Situationists' identity.

The group then shifted into its better-known and more theoretical phase, during which Debord developed his critique of the spectacle in the age of mass consumption, culminating in the publication of The Society of the Spectacle in 1967. The following year, the largely student-led protest movements throughout Europe drew heavily from the SI's theoretical and critical framework, referencing Debord's book, Belgian Situationist Raoul Vaneigem's The Revolution of Everyday Life (1967), and Tunisian Situationist Mustafa Khayati's On the Poverty of Student Life (1966). By 1972 the SI had dissolved, leaving Debord and Italian writer Gianfranco Sanguinetti as the last two official members.

The collection is organized into chapters related to specific individual SI members and events as well as related groups, including the Spur group and the Scandinavian Drakabygget group, which went on to publish a "journal for art against atomic bombs, popes and politicians." Though both groups were expelled from the official SI in 1962, they continued to operate as Situationists on their own terms. Indeed, one of the collection's strengths is that it allows for a more inclusive consideration of Situationists, ranging beyond Debord's orthodoxy to include Jorn, Jacqueline de Jong, Piero Simondo, and other figures as well as the various branches active across Northern Europe. Each chapter consists of a mix of visual and manuscript material, publications, and a large amount of ephemera.

Highlights include:

• Proof prints made by Asger Jorn for the artist's book Fin de Copenhague, as well as other prints by Jorn
• The postcard invitation for Yves Klein's 1957 exhibition at the Iris Clert Gallery, addressed to Jorn and featuring the fake stamp made by Klein, colored in his famous International Klein Blue
• An exact photocopy reproduction of three notebooks containing the manuscript for Debord's Society of the Spectacle (1967) and several handwritten letters from Debord
• The catalog and invitation for Destruction of the RSG-6, the only official Situationist exhibition
• Debord's extremely rare tract Remarques sur le concept d'art experimental (1957), hand-numbered 4 of 17
• Photographs of models and designs by Constant
• Photographs of the May 1968 Paris demonstrations

The SI collection reinforces related holdings already at the Research Institute including Guy Debord Letters Sent and Photographs, Internationale situationniste ephemera, Jean Brown Papers, L'Architecture Lettriste Collection, Lettrism Papers, Lettrist Movement Papers, and Manuscripts by Isidore Isou and Maurice Lemaiître. Above all, the collection allows for deeper research into SI's artistic and visual identities and makes clear the group's reach across Europe, while revealing connections to be made between the SI and other postwar figures and movements.