Autoclaved aqueous extracts of Candida albicans cells (and the glucans isolated from them) give a positive reaction with a chromogenic substrate combined with amebocyte lysates of the Japanese horseshoe crab, Tachypleus tridentatus (CS-TAL). The extracts and glucans activate the lysate enzyme compound G, which in turn activates clotting enzyme. Activated clotting enzyme causes a positive CS-TAL reaction. C. albicans extracts and glucans react positively with a commercially available, unaltered CS-TAL preparation (Toxicolor), but they give a negative reaction with a CS-TAL from which compound G has been excluded (Endospecy). An autoclaved, sterile preparation of Sabouraud glucose broth used as a control in one experiment gave (like Candida extracts) a positive reaction with Toxicolor and a negative reaction with Endospecy. We found that the peptone powder used to make the Sabouraud glucose broth was contaminated with a strain of Bacillus subtilis. Autoclaved aqueous extracts of culture-grown B. subtilis cells were positive with Toxicolor and negative with Endospecy. This was also the case with two other strains of B. subtilis. Polysaccharides obtained from these extracts gave the same result. Endotoxin activates clotting enzyme through activation of the lysate enzyme compound C, which is present in both Toxicolor and Endospecy. Endotoxin, therefore, reacts with both CS-TAL preparations. Simultaneous assay with Toxicolor and Endospecy distinguishes endotoxin from fungal products, but since products of fungi and B. subtilis both give a positive Toxicolor and a negative Endospecy test, a simultaneous assay cannot differentiate them. However, this does not decrease the clinical value of the simultaneous Toxicolor-Endospecy assay for distinguishing fungal infection from endotoxemia because B. subtilis so rarely causes disease that it can be excluded from clinical consideration.