A global optimization method is presented for computing the minimum limit load factor of trusses subjected to unknown but bounded loads. We assume that the external forces consist of a part proportional to a load factor and a part that is uncertain around its nominal value. The worst-case limit load factor is introduced as the smallest limit load factor realized with some uncertain parameters. By reformulating the worst-case determination problem as a mixed 0-1 programming problem, we propose a global optimization algorithm by a combination of a branch-and-bound method based on the linear programming relaxations and a cutting plane method based on the disjunctive cuts.