Picogram quantifies per ml of endotoxin showed a positive limulus test. The concentration more than ten pg/ml of curdlan ((1-3)-beta-D-glucan) was also positive to a conventional limulus test, which contains a factor G. One nanogram per ml of CM-curdlan was positive, but higher concentration of 10 pg/ml of CM-curdlan decreased its optical density of the conventional limulus test. More than one hundred ng/ml of mannan from Saccharomyces cerevisiae did not react with factor G. However, a culture supernatant of Saccharomyces cerevisiae activated factor G. This result suggested that beta-glucan activated factor G. In addition, culture supernatant of Aspergillus fumigatus, Rhodotorula rubra, Candida parapsilosis, Candida tropicalis, Candida krusei also activated factor G, but Cryptococcus neoformans did not activate it.