The purpose of this study was to theoretically base, develop, and test items for the Stimulus Intensity Modulation Scale (SIMS) which was intended for use in healthy as well as ill populations. According to stimulus intensity modulation theory, persons vary in their need for stimuli, depending on their nervous system's ability to modulate sensory stimuli. Content validity was established for the SIMS and a principle component extraction with varimax rotation resulted in a three-factor solution supporting the theoretical factors of pain tolerance, attention and habituation. Item analysis resulted in a final scale of 27 items. An internal consistency of .81 was achieved for the overall SIMS. Respective subscale coefficients of .82, .74, and .63 were obtained. Test-retest coefficients of .92, .83, .79 and .95 for the total scale and its subscales, respectively, were obtained over a 1-month period. Discriminant validity and freedom from socially desirable response bias was also accomplished.