Changes in the composition of the cellular lipid pool are known to occur in response to various stimuli during cellular activation. However, long-term changes in the composition of this pool associated with the chronic inflammatory reaction, as seen in byssinosis, have not been assessed. Last year at this meeting we presented a method for the rapid screening of the fatty acids obtained from lung lavage involving Fast Atom Bombardment Mass Spectrometry. We now present data regarding improvements in that methodology as well as preliminary data on the relative composition of fatty acids in the cellular fraction of bronchoscopic lung lavage samples obtained from human airways.