In order to engage parents or children as agents of change to increase physical activity (PA) at the family level, it is critical to understand the relationship between parent and child PA. PURPOSE: To employ high-frequency accelerometry (ACC) to explore parent-child PA correlations across a large sample of free-living data. METHODS: During the Fall of 2012 and Fall/Spring of 2013, we recorded seven days of free-living, wrist-mounted ACC data (75 Hz; GENEActiv) collected at up to 3 time points from 191 fourth and fifth grade children and their parents (n=382) who were participants in a school- and family-based obesity prevention program. For the present analyses, we considered baseline data. One-hundred and fifteen dyads had one observation, 46 dyads had two observations, and 30 dyads had 3 observations, totaling 297 paired observations. Using a custom Matlab program, we summed child and parent accelerations over 1 and 60 seconds, respectively, and applied published GENEActiv cutpoints to determine the amount of time spent in moderate-vigorous PA (MVPA) during the weekday, weekend day, and specific time periods (before school, school-day, after school, and evening). Bivariate correlations were run to explore the parent-child relationship between percent of time spent in MVPA. RESULTS: Weak positive correlations were observed between the percent of time parents and children engaged in MVPA during weekdays (r=0.142, p=0.014) and weekend days (r=0.235, p<0.001). Additionally, the before school (r=0.352, p<0.001) and after school (r=0.121, p=0.038) time periods also demonstrated significant positive correlations between parent and child PA accumulation, but no such correlations were observed during the school-day or evening. CONCLUSION: Based on the overall weak correlation in PA between parent-child pairs, these data suggest that parents or children alone might not be successful agents of change for the entire family. Additionally, it does not appear that parent and child PA is correlated during time periods that parents and children are apart (i.e., school-day). However, our data suggest that parent-child PA correlations are strongest during the before school period, which might be explained by active transportation. Supported by: Agriculture and Food Research Initiative Grant no. 2012-68001-19603 from the USDA.