The acute toxicity of Paecilomyces sinclairii was tested in beagle dogs. We daily examined clinical signs, body weights, and hematological/biochemical examinations for 14 days after administration of Paecilomyces sinclairii with different dose levels (0, 0.4, 2 and 10 g/kg). There were no clinical signs and no significant changes in hematological and biochemical analysis. These results showed that Paecilomyces sinclairii did not induce any remarkable acute toxic response and the $LD_{50}$ was greater than 10 g/kg in beagle dogs.