Background: Use of television, computers, and video games competes with physical activity and may be a health risk factor. Purpose: This study assessed the relationship between leisure-based screen time and physical activity in families to determine whether assignment to a limited screen time group results in more physical activity. Methods: Ninety-four families participated for six weeks. Families were randomly assigned to unlimited or limited screen time viewing groups. Participants wore a pedometer to measure steps. Results: Results indicate no statistically significant differences in steps for adults (F(1,165) = 0.81, p less than or equal to 0.369) or 13-to-18-year-olds (F(1,63) = 0.21, p less than or equal to 0.647). Among the 5-to-12-year-olds, statistically significant group differences (F(1,165) = 5.63, p less than or equal 0.019) for steps were found between the unlimited viewing group and the limited viewing groups. Discussion: Lower amounts of leisure-based screen time yielded increased amounts of physical activity in the 5-to-12-year-olds, but this trend was not found in the 13-to-18-year-olds or adults. Additional research is needed in order to more fully understand the screen time and physical activity relationship. Translation to Health Education Practice: In general, promotion of physical activity at home and school could increase physical activity and decrease leisure-based screen time; otherwise, other sedentary activities may only replace the time not spent in front of a screen. (Contains 3 tables.)