The purpose of the present study was to investigate the effects of a rest period on kindergartners’ performance in a simple reaction time situation. Effects of sex, class, time of measurement and practice on simple reaction time were also factors investigated in the present study. The sample consisted of 32 children ranging in chronological age from 62 months to 74 months. The children were enrolled in kindergarten at Pembroke Elementary School, Giles County, Virginia. Data were collected over 20 days with seven additional days for make-up. An overall analysis of variance was performed to determine any significant differences in reaction time. Males were significantly faster than female subjects in one class but not in the other. The subjects reacted slower in both classes as the day progressed. The subjects in Class One reacted slower between the morning and pre-rest periods. For both classes, subjects reacted slower after a rest than before a rest. Results were discussed in relation to the findings of the study. / Master of Science