Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy in children. Paralysis of respiratory muscles causes a decrease in forced vital capacity (FVC) from age 12 years, and death occurs between 20 and 25 years old and is usually related to respiratory insufficiency. Uncontrolled studies suggest that early home use of nasal intermittent positive-pressure ventilation (NIPPV) in DMD patients free of respiratory failure could limit progression of the restrictive syndrome and therefore improve survival because efficacy of preventive NIPPV has not been demonstrated in a controlled trial, we undertook a randomised multicentre study in which 70 patients with DMD were included. Patients were free of daytime respiratory failure and FVC was between 20 and 50% of predicted values. At least 6 h of nocturnal NIPPV (n = 35) was compared with conventional treatment (n = 35). During a mean follow-up of 52 months, 10 patients died, 8 in the NIPPV group and 2 in the control group (p = 0.05, log-rank test). No differences were observed between the two groups for occurrence of hypercapnia, decrease of FVC below 20% of initial values, or use of necessary mechanical ventilation. Preventive NIPPV did not improve respiratory handicap and reduced survival of DMD patients. Use of NIPPV for preventive purposes should be avoided in patients with FVC between 20 and 50% of predicted values.