Fatal cases of farmer's lung (FL) are rare. We found, based on death certificates, 13 cases of FL with a fatal outcome in Finland between 1980 and 1990. Compared with incidence data from the years 1980 to 1982, the mortality was estimated as 0.7 percent. On average, death occurred 8 years after the diagnosis of FL. One patient died acutely after a heavy mold exposure. The other patients had chronic disease. Among them the immediate cause of death was pneumonia in seven patients, respiratory insufficiency in four, and pneumothorax in one patient. The majority of these patients with a fatal outcome had suffered from symptoms of FL for more than 1 year before the diagnosis was established and fibrotic changes were already visible in the chest radiograph at the time of the diagnosis.