The effect of an intravenous bolus injection of endotoxin, 0.1, 1 or 10 micrograms/kg, on rectal temperature, clinical appearance, haematological parameters, and on gastrointestinal electrical activity was examined in 11 conscious piglets of 4-5 weeks of age, with implanted electrodes in the antrum pylori, duodenum, jejunum and ileum. All doses resulted in a significant and dose-dependent increase in rectal temperature, in pronounced clinical signs and in distinct changes in haematological values. These included shivering, depression, respiratory distress, a leukopenia (0.1 micrograms/kg) or a leukocytosis (1 microgram/kg) with a shift to the left, an accelerated sedimentation rate and a decreased packed cell volume. Doses of 1 and 10 micrograms/kg induced a transient inhibition of gastroduodenal electrical activity. These results suggest that, in the piglet, endotoxin primarily manifests general clinical signs and that the gastrointestinal effects coincide with these.