The question of whether pupil diameter indicates information processing load during reading was investigated in three experiments involving 24 college students reading passages of varying difficulty. A TV camera and monitor, together with a video-recorder, were used to measure the diameter of the pupil under a reading condition and under three control conditions. No evidence was obtained which would suggest that the pupil dilates while reading. The generality of these results was investigated by measuring the pupil size of 20 college students while listening to tape recordings of the reading passages. No evidence was obtained which suggested that the pupil dilates while listening. These results suggested that pupil size cannot be used as an objective indication of whether or not an individual is, in fact, processing the information contained in connected discourse while he is supposedly engaged in reading or listening activities. Tables and references are included. (BT/author)