- Born in 1948 in Cape Town, South Africa
- Studied fine art at the University of Cape Town (1966-9).
- Jantjes left South Africa in 1970 after being awarded a DAAD scholarship to study at the Staatliche Hochschule für bildende Künste in Hamburg, Germany (1970-2).
- Jantjes was a founding member of the German anti-apartheid movement, he served for a time as consultant to the United Nations High Commissioner for Refugees.
- Jantjes settled in London in 1982, where he curated a number of exhibitions and lectured often.
- Jantjes served on the advisory board of the Tate Liverpool from 1992 until 1995, and was a trustee of London’s Serpentine Gallery from 1995 until 1998.
- From 1986 until 1990 Jantjes was a member of the Arts Council of Great Britain, and served as its consultant for the creation of the Institute of New International Visual Art (INIVA).
- Jantjes became artistic director of Oslo‘s Henie-Onstad Kunstsenter in 1998, and he currently lives in the Norwegian capital.
His works are displayed in public and private collections such as the Victoria and Albert Museum, London; Arts Council of Great Britain, London; Wolverhampton City Art Gallery, Great Britain; Coventry City Museum and the National Museum of African Art at the Smithsonian Institution, Washington D.C., USA.