Surveys of cow-calf producers indicate that undifferentiated bovine respiratory disease (BRD) in preweaned beef calves is recognized on approximately 20% of operations. In the US, BRD is reported to be the leading cause of death in preweaning calves 3 weeks of age and older. As compared to feedlot BRD or dairy calf BRD, relatively little information has been published regarding the epidemiology of preweaning beef calf BRD, or risk factors for the problem. However, the available information indicates that the annual incidence of preweaning calf BRD varies significantly between herds, and between years in herds that experience the problem. Calves identified with preweaning BRD have been found to weigh less at weaning than calves not identified with preweaning BRD. While more research is needed, evidence available to date indicates that at the calf level, male calves, calves born with a twin, calves born to a heifer, and calves that experience dystocia requiring major assistance are at increased risk for preweaning BRD. At the herd level, factors that have been associated with pre weaning calf BRD include those that may 1) increase the opportunity for introduction of pathogens new to the herd; 2) increase susceptibility of calves to infection; and/or 3) increase opportunity for close contact among cows and calves within the herd. Because risk factors to date have been identified in cross-sectional surveys and thus are not necessarily causative, more research is needed to confirm the factors that cause preweaning calf BRD, and to identify practices that can mitigate the disease in herds where it is a problem.