Possible cytological changes of the conjunctival fluid in association with physical activity were studied in a series of 39 subjects practising aerobics, 22 football players, and 29 marathon runners by means of the quantitative pipette method and the qualitative stix method of Norn. The first group was only examined after exercise, the two latter both before and after. No significant changes were detected in the cytologic composition of the conjunctival fluid in association with exercise.