Endospecy (a lyophilized mixture of factor G-free limulus coagulation enzymes and chromogenic substrate, Boc-Leu-Gly-Arg-pNA) coupled with modified perchloric acid (PCA) pretreatment was carried out for the quantitative measurement of endotoxin in canine plasma. The endotoxin recovery from normal canine plasma was 99.9 +/- 7.7% (n = 20). The full recovery of endotoxin illustrated the applicability of the modified PCA pretreatment to the Endospecy in removal of interfering factors in a canine plasma. The normal canine plasma endotoxin level was less than 3.0 pg.ml-1 when Escherichia coli 0111:B4 endotoxin was used as a reference. The canine plasma endotoxin levels were markedly high(1-40 ng.ml-1) at 5 min after intravenous administration of 25 micrograms.Kg-1 (total 150-200 micrograms).