OBJECTIVE: To study the effect of samples having different pH values in the bacterial endotoxins test (BET). METHODS: The BET was conducted as an assay of the concentration of endotoxins by using kinetic-turbidimetric technique. Samples having different pH values but containing same concentration reference standard endotoxin (RSE) were tested by TAL/LAL reagents. The average result on the standard curve was calculated and the mean recovery observed. RESULTS: The reagents had three highly sensitivities in pH 5.20, pH 7.83/pH 6.23 and pH 10.55. After adjustment to pH 6 to 8, the mean recovery was 76.5%～115.9% or 85.8%～99.8%. When the sample pH value was less than 3 or more than 12, the test was unsuitable for the inhibition test, and the mean recovery was less than 56.8%. CONCLUSION: It is necessary to adjust the pH of the solution to be tested in the BET, adjust the sample to pH (6.5～7.5) when using TAL reagents, and adjust to pH (6.2±0.1) or pH(6.7～7.8) when using LAL reagents.