Rupf first met Paul Klee in 1913. At Rupf’s suggestion, Kahnweiler began representing Paul Klee in 1933. From 1946 onwards, Rupf committed himself to conserving Klee’s estate, which is unsurprising since Klee was a focal point of his collection.

Rupf had been in contact with Klee’s friend Wassily Kandinsky since 1931 – taking responsibility for his finances. Kahnweiler reported on Kandinsky’s funeral in a letter from December 1944. Rupf and Nina Kandinsky remained in contact.

A contract between André Masson and Kahnweiler had existed since around 1922. Rupf found it difficult to come to terms with the sometimes cruel aspects of Masson’s Surrealism – leading, around 1960, to him selling Massacre dans les champs (1933), while still retaining an important group of paintings and works on paper.