In an investigation of the relationship between atmospheric dust levels and worker health, the respiratory dust exposures of employees at two Saskatchewan potash mines were examined following atmospheric measurements. Some, notably those of the mining crew and the screening operators, were above the Threshold Limit Value 8-hour Time Weighted Average (TLV-TWA) for total nuisance particulates specified by the American Conference of Governmental Industrial Hygienists (ACGIH). Respiratory symptoms were recorded and forced expiratory lung function tests were done among 850 volunteers drawn from an eligible work force of 931. The results were compared between low and higher exposure groups after allowing for personal factors such as age and smoking habits. Symptoms of Grade I chronic phlegm production and mild shortness of breath and chronic cough were more common in the higher exposure groups, but episodes of chest illness were not. Severe respiratory symptoms were rare. There were no statistically significant differences in the proportions performing lung function tests below predicted values.