The objective of this study was to investigate the effect of screwdriver handle design and blade length on maximum torque and muscle activity. Five handle types and three blade length were evaluated. Twenty student subjects (10 males and 10 females) participated in this study. The subjects exerted maximum torque before and after screwing task. Physiological cost was simultaneously measured by electromyographic activities of 2 muscles (biceps brachii and flexor digitorum). The results indicate that handle effect was significant on anterior, posterior maximum torque (p < 0.001), and %MVC of biceps brachii muscle (p < 0.01). On the other hand, the effect of blade length was not significant on all measures. When the diameter of handle was greater, the MVC in anterior and posterior maximum torque exertion was increased, and the %MVC was decreased. The mean anterior and posterior maximum torque of females was 64 % and 62 % of that of males respectively.