Background: The primary purpose of this study was to investigate patterns of noncompliance in an adolescent field based accelerometer study. A further purpose was to investigate the effect of a cost efficient strategy (SMS reminder message) on the compliance of adolescents Method: The research carried out in 2010 involved 117 second level students (12.41 ± .53 yrs) from 4 schools in a rural Irish town. The Actigraph accelerometer data were processed over 7 days to determine compliance level. Results: Students were more likely to remove their monitor in the evening period than at any other time, however if students removed their monitor after school it remained unworn for a significantly longer duration than in any other time period. Students who received a SMS message were significantly more likely (P = .008) to wear their monitor in the morning than those that did not. Conclusions: Sending an SMS message each morning is effective for improving the number of students wearing monitors to school. The after school period is a critical period for nonwear time and should be targeted in future studies wishing to improve compliance. © 2013 Human Kinetics, Inc.