Objective. Report frequencies of adolescents' active commuting to school in an inner city environment in the Netherlands, and to explore potential socio-demographic correlates of active commuting to school. Methods. Cross-sectional data were obtained from the ENDORSE study (2005-2006) including 1361 adolescents (response=82%), aged 12-15 from 16 schools in Rotterdam. Socio-demographic variables were assessed by questionnaire. height and weight were measured and distance to school was calculated based on route planner information. Multilevel logistic regressions were performed to analyze the data. Results. The proportions of participants categorized as walkers, cyclists, non-active commuters were 12%, 35% and 34% respectively. With cyclists as the reference category, adolescents of non-Western ethnic background were more likely to be walkers (OR=4.1; 95% CI=2.1-8.2) and non-active commuters (OR=5.1; 95% CI=3.3-7.9), compared to native Dutch adolescents. A further distance from home to school was inversely associated with being a walker (OR=0.22; 95% CI=0.17-0.29) and being a cyclist (OR=0.83; 95% CI=0.79-0.86) and positively associated with being a non-active commuter (OR=1.2; 95% CI=1.16-1.23). Conclusion. Almost 50% of the adolescents reported to actively commute to school on most school days, and mode of commuting was associated with ethnicity and distance. Further research is needed to examine main barriers to active commuting among adolescents from non-Western ethnic background. (C) 2008 Elsevier Inc. All rights reserved.