Describes a procedure for using the Kinetic Turbidimetric Limulus Amebocyte Lysate (LAL) method to determine endotoxin levels in water, media, bulk intermediates and final products. Procedure employs ThermoMax Microplate Reader and SoftMax instrument control software from Molecular Devices. Includes an attached data collection form, "ThermoMax Endotoxin Determination Logsheet." Referenced sources include USP 23:85 "Bacterial Endotoxin Test," BioWhittaker's "LAL Review," and FDA's "4.3 Guideline for Validation of the Limulus Amebocyte Lysate Test as an End-Product Endotoxin Test for Human and Animal Parenteral Drugs, Biological Products, and Medical Devices."