The relation between relative humidity at the place of work and subjective discomfort as well as a number of objective parameters was studied in 34 contact lens wearers. Subjects in a low relative humidity (less than about 30%) showed significantly shorter BUT on the lens and more prominent lens deposits than subjects in a higher relative humidity (greater than 40%). A short BUT on the lens was associated with lens deposits (and vice versa) and restricted lens movements. Discomfort was particularly prominent when humidity was less than about 25%, when BUT on the lens was less than 20 sec, and when lens deposits were present. An experiment where relative humidity was manipulated between about 20 and 50% showed that subjects with a short BUT on the lens and prominent lens deposits were much more sensitive to a low relative humidity than other subjects. Enzymatic cleaners, frequent lens replacements, and loose fits were valuable to lessen discomfort.