Studies on personal dust and endotoxin concentrations among animal farmers have been either small or limited to a few sectors in their investigations. The present study aimed to provide comparable information on the levels and variability of exposure to personal dust and endotoxin in different types of animal farmers. 507 personal inhalable dust samples were collected from 327 farmers employed in 54 pig, 26 dairy, 3 poultry, and 3 mink farms in Denmark. Measurements in pig and dairy farmers were full-shift and performed during summer and winter, while poultry and mink farmers were monitored during 4 well-defined production stages. The collected samples were measured for dust gravimetrically and analyzed for endotoxin by the Limulus amebocyte lysate assay. Simple statistics and random-effect analysis were used to describe the levels and the variability in measured dust and endotoxin exposure concentrations. Measured inhalable dust levels had an overall geometric mean of 2.5 mg m(-3) (range <LOD to 47.8) and endotoxin of 988 EU m(-3) (range <LOD to 374,000). The highest dust and endotoxin concentrations were measured among pig and poultry farmers, and were the lowest among dairy and mink farmers, respectively. Exposure among pig and cattle farmers was characterised by a substantial day-to-day variability that increased from the indoor to outdoor working environment. Only mink farmers complied with the Danish occupational exposure limit for total dust (3 mg m(-3)). More than 93% of our measurements exceeded the recently proposed Dutch exposure-limit for endotoxin (90 EU m(-3)). These findings suggest animal farmers to be exposed to high levels of dust and endotoxin consistent with an increased risk of developing respiratory symptoms and diseases. The development of preventive strategies to reduce exposure will require in-depth identification of factors that affect day-to-day variability in exposure.