A case study was conducted using an automatic sphygmomanometer to compare stress encountered by workers using two different machine actuation safety devices. Six female power press operators, aged 21 to 59 years, were examined. Blood pressure cuffs were placed on the ankles of the operators and were controlled by a microprocessor. Blood pressure measurements were transmitted and were based on pulse wave amplitude during obstructing steps. Heart rate was also determined. Each subject spent 2 working days operating a press equipped with each of the two control modes. Prior to and after the work day, a measure was made of baseline and recovery blood pressure and heart rate. Subjects were sampled at 8 and 10 minute intervals throughout job performance. At the end of each day a feeling tone check list questionnaire was answered by each subject. The selected stress measures included mean blood pressure, systolic blood pressure, diastolic blood pressure, and heart rate. The stress measures varied from 0.7 to 1.8 percent between the self tripping and two hand control actuation modes. The differences were not statistically significant nor were they clinically meaningful. No significant responses were obtained for the feeling tone check list. Operators produced 30 percent more parts using the self tripping system at the same amount of stress. The authors conclude that for the small population tested, there is no significant difference in the stress measures examined.