Trona (sodium sesquicarbonate) is mined from an underground deposit in Wyoming and processed for use in the manufacture of glass, paper, and detergents, and in chemical applications. Trona dust is alkaline (pH 10.5) and may have an irritant effect on the respiratory airways, mucous membranes, and the skin. One hundred forty-two underground miners and 88 surface workers from one trona facility participated voluntarily in an epidemiologic and clinical study. Their mean age was 37.6 and their mean working period, 10.0 years. One half of the study participants complained of skin symptoms; dermatologic symptoms increased from twofold to fifteenfold after the subjects began trona mining. Trona dermatitis consists of pruritic, erythematous, raised, dry, and fissured lesions commonly affecting the hands, arms, and legs. A dose-response relationship was observed among underground workers. Patch testing with 10% aqueous trona and sodium carbonate was negative, suggesting that the dermatitis was primarily irritant in nature.