Current bovine respiratory disease (BRD) diagnostic methods in the commercial feedlot setting are limited to subjective visual assessment of clinical signs; sensitivity and specificity of this method is poor. Continuous monitoring of step count, lying bouts, and duration of standing time via accelerometer device will provide insight into the behavior of clinically ill cattle and characterize the pattern of behavior change before clinical BRD diagnosis. Our primary objective was to elucidate behavior variable responses in relation to the timing of clinical disease observations by animal health technicians in a commercial feedlot, and compare behavior of cattle clinically diagnosed with BRD to a healthy cohort. A secondary objective was to determine BRD morbidity rate for cattle according to arrival castration status and initial body weight quartile. American Association of Bovine Practitioners Proceedings of the Annual Conference, 2015