Background: Pulmonary alveolar proteinosis (PAP) is a rare disease characterized by abnormal accumulation of lipoproteinaceous material within the alveoli. This study aims to compare clinical and laboratory features and therapeutic approach of PAP over the years. Methods: A total of 78 patients with PAP from 13 university hospitals registered in Korean Interstitial Lung Disease Research Group were included in this study. The patients were divided into two groups, based on the year of diagnosis: group A with patients diagnosed from 1993 to 2007 (n= 41) and group B diagnosed from 2008 to 2013 (n = 37). We compared group A and B using the data on demographics, smoking status, diagnostic methods, symptom at presentation, pulmonary function tests, and occupation and exposed dusts. Results: The median age at diagnosis was 41 years (range, 15-81) in group A and 48 years (range, 15-68) in group B (p=0.349). Male to female ratio was similar. In recent years, less number of patients received BAL and/or TBLB (90.2% vs 75.7%; p=0.085), while surgical lung biopsy (SLB) was performed in similar numbers (43.9% vs 45.9%; p=0.856). Although not significant, the incidence of PAP in never smoker was increased after 2008. A history of dust exposure was seen in 43.6% (39.0% vs. 48.6%; p=0.392). Thirty-five (44.9%) patients underwent whole lung lavage (WLL), which was used less in recent years (58.5% vs. 29.7%; p=0.011). Oxygenation (PaO2: n=23, p=0.016; DLco: n=13, p=0.089) markedly improved after WLL. Anti-GM CSF antibody treatment was used for 1 patient in group A (2.4%) and 3 patients in group B (8.1%; p=0.341). Overall survival was 96% (n=75). Conclusions: PAP is increasing in Korea. Dust exposure seems an important predisposing factor. WLL is a safe procedure and yields dramatic improvements in oxygenation in PAP.