Abstract Pulmonary alveolar proteinosis (PAP) is a rare disease, with several aetiologies. This study reports the first Finnish case of PAP with possible induction by silica dust. A 58-year-old male patient had a documented history of heavy exposure to silica dust over a long period, although he himself considered the exposure to be low. The patient's cumulative exposure to silica dust was approximately 10 mg m(-3) years according to the workplace measurements. The patient developed classical symptoms and signs of PAP that closely mimicked those of acute silicosis, but he did not have any signs of classic silicosis. We conclude that significant chronic exposure to silica favours the diagnosis of PAP rather than acute silicosis in this case. PAP should be taken into account when patients exposed to silica dust complain of respiratory symptoms. A patient's assessment of his/her exposure to silica may not always be reliable.