Children with leukaemia are at increased risk of pulmonary complications, often with unspecific clinical data, delayed diagnosis and a high mortality rate. We evaluated the usefulness of diagnostic-therapeutic guidelines (DTG) in which specific times for decision making were incorporated. Clinical charts of children with acute leukaemia and suspicion of pulmonary involvement were reviewed. Patients were allocated to group I if their diagnostic and therapeutic decisions were in accordance with the DTG, and to group II if not. Children from group I (n=32) and group II (n=28) did not differ with respect to age (9.3+/-0.5 years old, mean+/-SEM), gender, type, risk and stage of leukaemia, anaemia and neutropenia. Total length of hospital stay and hospitalization due to the pulmonary disease were shorter in group I than in group II (14.8+/-2.1 vs. 28.5+/-3.7 days, p=0.0016; and 10.8+/-1.0 vs. 18.4+/-1.8 days, p=0.0003, respectively). Two patients (6.3%) died due to the pulmonary pathology in group I, and nine (32.1%, p=0.016) in group II. Diagnostic-therapeutic guidelines that incorporate timely decisions constitute a useful algorithm to reduce the length of hospital stay and mortality in children with acute leukaemia and pulmonary infiltrates. A prospective study is needed to validate these results.