OBJECTIVE To study the association between physical activity energy expenditure (PAEE) and cardio-respiratory fitness (CRF) with key metabolic traits and anthropometric measures in the Tarahumara of Mexico. METHODS A cross-sectional study was carried out in five rural communities in Chihuahua, México including 64 adult Tarahumara, mean (SD) age 40.7 (12.9) years. Using a combined accelerometer and heart rate sensor, PAEE was measured over three consecutive days and nights and a sub-maximal step test was carried out in order to (1) calibrate heart rate at the individual level and (2) to estimate CRF. Random blood glucose level and resting blood pressure (BP) were measured with standard anthropometrics. RESULTS Mean (SD) PAEE was 71.2 (30.3) kJ kg(-1) day(-1) and CRF was 36.6 (6.5) mlO(2) min(-1) kg(-1) . Mean (SD) glucose was 127.9 (32.4) mg/dl, with 3.3% having diabetes. Mean (SD) systolic and diastolic BP was 122 (20.8) and 82 (14.8) mm Hg, respectively, with 28.1% having hypertension. Mean body mass index was 27.5 (4.2) kg m(-2) , with 71.9% being overweight. Following adjustment for age and sex, weak inverse associations were observed between PAEE and systolic BP (β = -0.20, P = 0.27) and diastolic BP (β = -0.16, P = 0.23); and between CRF and systolic BP (β = -0.51, P = 0.14) and diastolic BP (β = -0.53, P = 0.06). The inverse associations with glucose were also weak and not statistically significant for neither PAEE (β = -0.01, P = 0.63) nor CRF (β = -0.05, P = 0.27). CONCLUSIONS This study suggests high levels of overweight and hypertension in the Tarahumara, and points to fitness and physical activity as potential intervention targets although findings should be confirmed in larger samples.