Endotoxins liberated by gram-negative bacteria are frequent contaminants of aqueous and physiological solutions. Because of their potent biological effects in vivo and in vitro, their detection and removal are essential for the safe parenteral administration of products produced from natural sources, as well as those produced by recombinant DNA technology. Traditional methods of endotoxin detection include the U.S. Pharmacopeia rabbit test and the Limulus amebocyte lysate test. Elimination of endotoxins, however, continues to be a problem. Standard methods of sterilization, such as autoclaving or sterile filtration, have little effect on endotoxin levels. Various techniques for the prevention of endotoxin contamination and endotoxin removal have been discussed. The overall role of endotoxin prevention, detection, and elimination in biotechnology is emphasized.