Introduction. Pulmonary alveolar proteinosis is an uncommon disease characterized by the accumulation of surfactant proteins and phospholipids within the alveolar spaces. Acquired disease can be idiopathic (primary) and secondary. The prevalence of acquired pulmonary alveolar proteinosis is about 0.37 per 100,000 persons. Common symptoms are dyspnea and cough. Chest X-ray shows bilateral perihilar infiltrates. Open-lung biopsy is the gold standard for the diagnosis. Treatment includes whole-lung lavage, application of granulocyte-macrophage colonystimulating factor and lung transplantation. Case report. We reported a 51 year-old man with primary form of the disease. It was the second case of this extremely rare disease in the past 30 years in our clinic. The symptoms were longlasting dry cough, fever and physical deterioration. Chest Xray revealed bilateral pulmonary infiltrates; computed tomography showed patchy ground-glass opacification with interlobular thickening. The diagnosis was established by open lung biopsy. Additional tests were performed to exclude secondary form of the disease. Conclusion. We presented a rare clinical entity with typical clinical features and clinical and radiological course of the disease, in order to improve differential diagnostic approach to patients with bilateral lung infiltrations. In patients with pulmonary alveolar proteinosis timely diagnosis and adequate treatment can improve a prognosis.