Exposure to cotton dust causes an airways inflammation with Monday morning chest tightness and decreases in spirometry as hallmark effects. The response has been related to the content of endotoxin in the dust and symptoms of byssinosis have been reproduced after exposure to pure endotoxin. An important prerequisite for the effects of endotoxin is the binding to the cell surface. This takes place through interaction between endotoxin and the receptor CD14. A recent study described a polymorphism in the CD14 gene in terms of a single C: T substitution in the flanking region of the gene. The frequency of allele C was about 50% in a Caucasian population. Homozygotes for the C allele (C:C) and C:T heterozygotes had lower than normal serum levels of soluble CD14. Blood cells from these persons were also low producers of IFNg and high producers of IL-4 when stimulated in vitro. It is suggested that symptoms after inhalation of endotoxin and cotton dust are related to sCD14 polymorphism. Studies to test this hypothesis are in progress.