Summary: The xenoliths, which are gabbroic in character, consist of kaersutite, titanaugite, plagioclase, and iron ore in variable amounts. Biotite and olivine are also occasionally present. New analyses and trace element data are given for two xenoliths and their coexisting kaersutite, titanaugite, and plagioclase. After discussing several possible origins with the aid of a principal latent vector variation diagram, it is concluded that they represent the accumulation of phases that crystallized from the Tristan magma at depths between 5 and 25 km. Evidence is also presented to show that the parental Tristan magma may be of trachybasalt composition.