A survey was conducted on 300 lactating dairy cows on 10 dairy farms to determine how risk factors for and symptoms of excessive grain feeding and subacute ruminal acidosis are associated with the concentrations of endotoxins in feces measured with the Limulus amoebocyte lysate test. Increases in days in milk and haptoglobin in blood plasma were associated with lower (P=0.02) and higher (P=0.02) fecal endotoxin, respectively. The five farms with a dietary neutral detergent fibre (NDF) content higher than 33.8% of DM had lower (P<0.01) fecal endotoxin than those with a dietary NDF content lower than 33.8% of DM (31 790 vs. 69 276 endotoxin units (EU) g-1 of wet feces, P<0.01). Parity, milk yield, milk fat percentage, milk protein percentage, the blood plasma concentration of serum amyloid A, and the dietary content of physically effective fibre were not associated with the fecal endotoxin concentration.