An extensive field survey of subjective symptoms of fatigue revealed three characteristic patterns. One, in which ‘ drowsiness and dullness ’ predominated, was frequent both among those who reported many symptoms and those who reported few and was not characteristic of any particular type of work. A second, in which “ inability to concentrate ” was prominent, was more frequent among those who reported many symptoms and was characteristic of mental workers, especially after night work. A third pattern, in which awareness of physical discomfort was characteristic, was found mainly among those who reported few symptoms and were engaged in physical work.