During the calf component of the National Animal Health Monitoring System′s Dairy 2014 study, information was collected on morbidity and mortality in preweaned dairy heifers. In addition, data were collected on birthing parameters, serum IgG, and treatments administered. Data have been collected from 851 calves on 89 farms in 12 of the nation’s top dairy states. These results from the interim analysis are based on approximately 25% of the total number of calves expected to be enrolled in the study. The objective of the study was to assess morbidity and mortality of preweaned dairy heifers in the US to aid management decisions and increase heifer survival. Of the 851 calves, 33.4% experienced at least 1 disease event, and 6.1% had more than 1 disease event. The maximum number of disease events reported was 6. Clinical signs of morbidity were classified as dull; dehydrated; gastrointestinal; respiratory; lameness; and neurological. Gastrointestinal signs were observed in 18.0% of calves, while dullness was reported in 13.3% of calves and respiratory signs in 10.6%. Of the 33.4% of calves with clinical signs, 93.3% received treatment. Medications, including antibiotics, were administered to 82.4% of calves and electrolytes were administered to 35.6% of calves. Interestingly, of the 5.4% of calves that died, 39.1% died without displaying clinical signs before dying. The average age at death was 22.8 d, with a range from 3 to 78 d. Birthing parameters, including calving-ease score, number of calves born, and disinfection of the navel were not associated with morbidity or mortality. Serum IgG was collected and calves were classified as excellent ≥15.0 g/L (71.2%); fair 10.0–14.9 g/L (11.4%); or failure <10.0 g/L (17.4%) of passive transfer. Calves with fair passive transfer had higher levels of morbidity (44.3%) compared with calves with excellent passive transfer (30.4%). Serum IgG categories were not associated with mortality. High serum IgG levels were associated with decreased morbidity. Digestive and respiratory diseases were the 2 most common causes of morbidity in preweaned heifer calves.