The main objective is to assess whether nebulization before gastric lavage (GL) improves its sensitivity for the diagnosis of childhood tuberculosis (TB). Children and adolescents suspected of pulmonary TB were randomly assigned (1 : 2) to nebulization with hypertonic saline 30 min before GL (Neb group; n = 36) or GL without prior nebulization (controls; n = 68). The proportion of positive GL smears was greater in Neb group than in the control group; however, no statistical significance was observed (36.3% vs. 22.2%; p = 0.4). Inhalation of nebulized hypertonic saline before GL did not improve TB diagnosis in this study. Nevertheless, the validation of our data will require large longitudinal studies.