Abstract: In a method of determining the presence of an endotoxin or endotoxin-like material in a sample, a) a sample is incubated with a component of horseshoe crab amoebocytes lysate or haemolymph or a synthetic analogue thereof, b) the incubated mixture of the sample and the component or analogue resulting from step a) is reacted with an antibody raised against the component or analogue or against a reaction product of the incubation of step a), and c) the presence of endotoxin or endotoxin-like material in the sample is determined by detecting any bound antibody in the reaction mixture of step b). In the method either the component or analogue or the antibody or the endotoxin or endotoxin-like material is coupled to a solid support.