In 1986, researchers administered a respiratory health questionnaire to 4,656 Lancashire textile workers who were employed in 31 mills involved in the spinning or weaving of cotton fibrs. At the same time, tests measured levels of airborne cotton dust and bacteria in work zones on the mill floor. In all, 182 workers described symptoms characteristic of byssinosis. Compared with data from 1976, this represented a significant decline in the prevalence of byssinosis in Lancashire textile workers. Nevertheless, the 1986 data were statistically significant. The prevalence of byssinosis correlated with the number of years worked in the textile industry, ethnic origin, type of duty and dust exposure, quality of cotton, and smoking habits. The correlation between the presence of byssinosis and the concentration of total dust (less fiber fly) in work zones on the mill floor was highly significant (r = 0.92). Regressino analysis suggested that at airborne dust concentrations under 1.2 milligrams per cubic meter, less than 5 percent of mill workers will develop byssinosis. 8 refs.