This study investigated the effect of a 12-week pedometer-based intervention on daily step counts of 147 older adults randomly assigned to an intervention or wait-list control group (M age = 72.9 years, SD = 8.8). The intervention group significantly increased their daily step counts after 12 weeks (M = 639, SD = 2,239) and continued to significantly increase during a 12-week maintenance period (M = 680, SD = 1,721). The control group exhibited no change during the control period (M = -393, SD = 2,050) but had a significant increase in daily step counts (M = 1,580, SD = 2,305) when enrolled in the intervention. The pedometer-based intervention was effective in increasing participants' daily step counts. (Contains 2 figures and 1 table.)