Whole lung lavage (WLL) is still the gold-standard therapy for pulmonary alveolar proteinosis (PAP). The few studies on the duration of the effect of WLL, belonging to a rather remote period, show significant but transient benefits. In 21 patients with idiopathic PAP, the duration of any benefit and, in 16 of them, the time course of lung function improvement (at baseline, 1 week, 6 months, 1 yr and then every 2 yrs after WLL) were evaluated. The present WLL technique takes longer, is invasively monitored and partially modified with respect to past techniques. More than 70% of patients remained free from recurrent PAP at 7 yrs. The bulk of the improvement in spirometric results was almost completely gained in the immediate post-WLL period due to the efficient clearance of the alveoli. At a median of 5 yrs, recovery of diffusing capacity of the lung for carbon monoxide was incomplete (75 +/- 19% of the predicted value) and there were residual gas exchange abnormalities (alveolar to arterial oxygen tension difference 3.6 +/- 1.5 kPa (27 +/- 11 mmHg)) and exercise limitation, probably explained by engorgement of lymphatic vessels. In conclusion, whole lung lavage for idiopathic pulmonary alveolar proteinosis is currently a safe procedure in an experienced setting, and provides long-lasting benefits in the majority of patients.