Abstract: A system for measuring fitness for duty which includes a) a visual stimulus display b) eye monitoring equipment for measuring eye and eyelid movements c) a central processing unit and data storage device to collect and store the data from the eye monitoring equipment d) a data analysis device programmed to calculate one or more of the measures of blink latency, measures of the relative velocity of upper eyelid closing and opening movements during blinks, the product of the amplitude to velocity ratio of eyelid closing and opening, the duration of blinks, the variability of eyelid movements during blinks, the failure to respond appropriately with a voluntary blink following each said brief visual stimulus e) said data analysis device programmed to place the values for said measures into an algorithm for measuring fitness for duty.