ELA, Volume 3, pp. 23-30, March 1998, abstract. Ultrametric sets in Euclidean point spaces Miroslav Fiedler Finite sets S of points in a Euclidean space the mutual distances of which satisfy the ultrametric inequality r(A,B) =< max {r(A,C), r(C,B)} for all points in S are investigated and geometrically characterized. Inspired by results on ultrametric matrices and previous results on simplices, connections with so-called centered metric trees as well as with strongly isosceles right simplices are found.