To objectively measure the physical activity (PA) levels of children attending family day care programs. Methods: A total of 114 children from 47 family day care centers wore an accelerometer for the duration of their time in care. Time in moderate-to-vigorous PA (MVPA) and total PA was calculated using previously validated cut points. Results: Children accumulated 5.8 +/- 3.2 minutes of MVPA and 10.4 +/- 4.4 minutes of total PA per hour of attendance. Boys exhibited significantly higher levels of PA than girls. Among healthy weight children, 4- and 5-year-olds exhibited significantly higher levels of PA than 2- and 3-year-olds. Overweight and obese 4- and 5-year-olds exhibited significantly lower levels of PA than their healthy weight counterparts. Conclusions and Implications: Children attending family day care participate in low levels of PA during the child care day. The results highlight the need for effective programs to promote PA in family day care. (author abstract)