Abstract. The joint numerical range W (F ) of three hermitian 3-by-3 matrices F = (F 1 , F 2 , F 3 ) is a convex and compact subset in R 3 . We show that W (F ) is generically a three-dimensional oval. Assuming dim(W (F )) = 3, every one-or two-dimensional face of W (F ) is a segment or a filled ellipse. We prove that only ten configurations of these segments and ellipses are possible. We identify a triple F for each class and illustrate W (F ) using random matrices and dual varieties.