PURPOSE: To identify device-specific cadence (steps/min) thresholds associated with absolutely-defined moderate and vigorous intensity (3 and 6 metabolic equivalents [METs]) for the Actical (AC), ActiGraph GT9X (AG), activPAL 3 (AP), and StepWatch 3 (SW) accelerometers. METHODS: A sample of 75 young (21-40 years), 80 middle-aged (41-60 years), and 97 older (61-85 years) adults (N = 252, 49.6% women; mean [SD] BMI = 25.6 [3.6] kg/m2 and height = 169 [9] cm) completed 5-min treadmill walking bouts separated by 2-min rests. Bouts began at 0.5 mph and increased by 0.5 mph until participants: 1) naturally chose to run, 2) reached >75% of age-predicted maximum heart rate, or 3) reported a Borg rating of perceived exertion >13. Participants wore an AC and AG (waist), AP (thigh), and SW (ankle) to assess steps. Oxygen uptake (VO2) was measured with indirect calorimetry and converted to METs (VO2 / 3.5 mL/kg/min). Cadence and METs were averaged over the last 2 min of each bout. Device-specific cadence thresholds were identified for the total sample and each age group by selecting those minimizing Youden index summaries of Receiver Operator Characteristic (ROC) curves. RESULTS: Device-specific cadence thresholds associated with 3 METs were ~100 (range 95-102) steps/min, except those for the AG in young and older adults, and thresholds associated with 6 METs were ~120 (range 118-124) steps/min (Table 1). All area under the ROC curve (AUC) values were ≥0.90. Sensitivity and specificity values were ≥80% (Table 1). CONCLUSION: Device-specific cadence thresholds accurately classified moderate and vigorous intensity in adults across the lifespan. However, 3 MET thresholds for the AG were up to 14 steps/min lower (in older adults) than those of the other devices and those reported in studies using the criterion of directly-observed steps (~100 steps/min). Future studies are needed to evaluate the performance of these thresholds in free-living settings. Funded by NIH NIA Grant 5R01AG049024