"Burden of care" is a term that describes the effects of the multifaceted stressors associated with providing care to an ill family member. Descriptions of burden of care in acute care populations, such as families of patients who have had coronary artery bypass grafting, are very limited. The three purposes of this study were to describe the burden of care in families of coronary artery bypass grafting surgery patients, to compare the burden of care in families grouped by length of stay, and to provide evidence for the validity of the Caregiving Burden Scale in acute care populations. A survey was done using a longitudinal design over the first six weeks following coronary artery bypass grafting surgery. The 124 spouses of coronary artery bypass grafting surgery patients who participated reported a moderate degree of burden in caring for post cardiac surgery family members. Providing emotional support, taking over household tasks, and monitoring patients' conditions created the greatest burden for the participants. Length of stay in hospital did not have an impact on burden of care. The analysis of the data supports the validity of the Care-giving Burden Scale when used in the cardiac surgery population. (Prog Cardiovasc).