The volume 281 of Discrete Applied Mathematics, containing a special issue dedicated to LAGOS’17: IX Latin and American Algorithms, Graphs and Optimization Symposium, C.I.R.M., Marseille, France – 2017, has appeared online. It has been edited by Frédérique Bassino, Flavia Bonomo-Braberman, Lionel Pournin, and Mario Valencia-Pabon.