The cardiovascular stress effects of computer system response time and method of pay among workers performing a computer based data entry task were investigated. Subjects included 45 female professional typists, recruited from an agency. Subjects entered records from paper copy into a computerized database by video display terminal. Subjects worked under one of four conditions: rapid response time/nonincentive pay; slow response time/nonincentive pay; rapid response time/incentive pay; and slow response time/incentive pay. The results of the study indicated that performing a data entry task under computer administered incentive pay conditions causes a pattern of stress related cardiovascular reactivity. Compared to nonincentive pay, incentive pay resulted in a significant reduction in heart rate variability and increased blood pressure across workdays. The findings suggested that under nonincentive pay conditions, slow response time does not change cardiovascular functioning. However, the lack of a slow response time effect under the more demanding incentive pay conditions was rather surprising and difficult to comprehend. One possible explanation was that the electronic feedback of incentive pay earnings reduced the performance uncertainty or stress associated with system delays, and thereby minimized any cardiovascular stress effects. The temporal effects occurred irrespective of response time and method of pay, and they were indicative of reduced effort or increased mental fatigue associated with performing the data entry task for sustained periods of time. An increase in heart rate and systolic blood pressure with a decrease in heart rate variability was noted from the morning to the afternoon work session.