Significance: Daily physical activity is an important health goal for children. The purpose of the study was to evaluate the effectiveness and convenience of Take10, a daily 10-min classroom activity break in elementary school children. Design: Take10 was implemented over a school year in all classes in one elementary school. Teachers were trained prior to starting Take10, and daily support was provided. Half of the classes (n = 12) served as controls (C) in the fall, and the other classes (n = 12) conducted Take10 (T10). In the spring, C classes also participated in the Take10 program. All children with parental consent wore an RT3 accelerometer for one week, in the fall semester and also in the spring semester. Teachers recorded times of Take10, recess, and P.E. every day during the week accelerometer data were obtained. At the end of the year, teachers also completed an evaluation survey. Children's accelerometer data (expressed as counts/min) were analyzed by either a 2-way mixed ANOVA or a series of 1-way repeated measures ANOVAs, depending on the research question. Significance tests were conducted at the p = .05 level, and controlled for multiple comparisons. Class-level data were analyzed descriptively. Results: Overall activity was not influenced by implementation of the Take10 program; overall counts/min of the C classes were not significantly different from T10 classes, and overall counts/min of the C class did not significantly change after beginning the Take10 program. There was no compensatory effect of Take10 on children's recess activity; recess counts/min were not significantly different when classes implemented Take10 than when Take10 was not implemented. Comparisons of activity during Take10 with activity during recess and P.E. were equivocal; during Fall counts/min were highest in P.E., then recess, and were lowest during Take10. In Spring, counts/min were highest in recess, then Take10, and P.E. was lowest. Most teachers gave positive evaluations of Take10 (ease of administration, adequacy of training and materials, response of children, intention to continue). However, daily records indicated that Take10 often replaced recess, and that Take10 was implemented an average of only 2.5 times per week. In summary, despite extensive daily support, favorable teacher response, and positive teacher evaluations, it appears that implementation of Take10 is difficult for teachers, and that overall activity of children is unaffected. Future research should address the reasons for compliance/noncompliance of classroom teachers to implementing daily physical activity for school children.Keyword(s): elementary education, physical activity, research