We examined the association of physical activity (PA), cardiovascular fitness (CVF) and fatness with total homocysteine (tHcy) concentrations in European adolescents. The present study comprised 713 European adolescents aged 14.8 +/- 1.2 y (females 55.3%) from the multicenter HELENA cross-sectional study. PA was assessed through accelerometry, CVF by the 20-m shuttle run test, and body fat by skinfold thicknesses with the Slaughter equation. Plasma folate, cobalamin, and tHcy concentrations were measured. To examine the association of tHcy with PA, CVF. and fatness after controlling for a set of confounders including age, maturity, folate, cobalamin, creatinine. smoking, supplement use, and methylenetetrahydrofolate reductase 677 genotype (CC 47%, CT 43%. TT 10%). bivariate correlations followed by multiple regression models were performed. In the bivariate correlation analysis. tHcy concentrations were slightly negatively correlated (p<0.05) with CVF in females (measured both by stages: r=-0.118 and by VO(2)max: r=-0.102) and positively with body mass index (r=0.100). However, daily time spent with moderate and vigorous PA showed a weak positive association with tHcy in females (p<0.05). tHcy concentrations showed a tendency to decrease with increasing CVF and increase with increasing BMI in female European adolescents. However. tHcy concentrations were positively associated with moderate and vigorous PA in female European adolescents.