686 textile operatives employed in five cotton and two manmade fibre mills have performed three data sets of reproducible measurements of lung function. These readings were recorded at yearly intervals over a three year period. The operatives employed in manmade fibre exhibited a greater decline in the mean Fev1 over the three year period (-31mls/yr CI=-14,-48 compared to -10mls/yr CI=4,-24). Smokers and ex-smokers in cotton had greater lung function declines compared to life long non-smokers. However, within manmade fibre an excess of decline was found in non-smokers compared to ex-smokers/smokers. Analysis by year demonstrated an overall increase in Fev1 mean 10mls (CI = -9; +29) between the 1st and 2nd lung function data sets. Between the 2nd and 3rd data sets a decline in lung function was found (mean 46mls CI=-26,-66). This data demonstrates a possible learning effect of spirometry technique in this group of textile workers and a possible excess decline in lung function in MMF workers.