The effect of video display unit (VDU) text-presentation rates on the reading speed and comprehension of 90 undergraduate psychology students was investigated. A modified version of a Nelson-Denny Reading Test comprehension subtest was presented to each subject at a rate of 150, 300, 1200, or 9600 baud, or in an "instant" condition which presented text one VDU "page" at a time. Comprehension scores were highest in the 300-baud and  Instant conditions, and lowest in the 150-baud and 9600-baud  conditions. VDU reading speeds were marginally higher in the 9600-baud condition, and marginally lower in the 150-baud condition.  In general, other timing measures were equivalent across conditions . At very high or low presentation rates, comprehension deteriorated. The ,mediating effect of three task characteristics was discussed: hurried or incomplete reading; the contect of timed performance; the stimulation of interactive computer use. No evidence was found that low rates enhance performance.