a b s t r a c tIn this paper, we continue the study of locating-total domination in graphs, introduced by Haynes et al. [T.W. Haynes, M.A. Henning, J. Howard, Locating and total dominating sets in trees, Discrete Applied Mathematics 154 (8) (2006) 1293-1300]. A total dominating set S in a graph G = (V , E) is a locating-total dominating set of G if, for every pair of distinct vertices u andThe minimum cardinality of a locating-total dominating set is the locating-total domination number γ L t (G). We show that, for a tree T of order n ≥ 3 with l leaves and s support vertices, n+l+1Moreover, we constructively characterize the extremal trees achieving these bounds.