Practical, rapid, noninvasive methods for assessing health status and establishing endpoints are needed in mouse experiments in which wasting and death are a potential endpoint, including aging and toxicology studies, ascites production, and phenotype analysis in mutant mouse colonies. Current methods for assessing the health status of a mouse and establishing endpoints might include observation of behavior, assessment of physical appearance, and measurement of body weight (BW). Behavioral parameters include observation of unprovoked behavior and responses to external stimuli. Classic changes in physical appearance include exophthalmia or enophthalmia (bulging or sunken eyes, respectively), nasal or ocular discharge, rough coat, and hunched back. These observations, as well as additional ones particular to an experimental procedure or to the genetic makeup of an animal, have been suggested as standard indicators of ill health (1–4). These clinical indicators can be scored as degree-of-deviation-from-normal, thereby allowing an animal to be monitored over time as health declines (1–4). Decreased food and water consumption is an important sign of deteriorating health (4), which generally results in loss of BW; support for using weight loss as an indicator of poor health in rodents comes from the study by Redgate et al.(5). They determined that 7 or more consecutive days of weight loss in central nervous system tumor-bearing rats correlated well with irreversible progression to death. However, Beynen et al.(2) found that observation of behavior and physical appearance was largely ineffective for discriminating between gallstone-bearing mice and healthy controls, and weight loss was significantly different between the two groups of mice for the males but not the females. They concluded that response to palpation of the right hypochondrium (ie, signs of a painful response) was the best indicator of gallstones for males and females. Twenty percent loss of rodent BW or prolonged weight loss (progressing to an emaciated state) are generally established criteria for euthanasia (3, 6). However, there are practical problems with the measurement of BW, which may not yield an accurate measure of fat stores and muscle mass, because reduction of fat stores and muscle mass (as measured by BW) is masked if weight loss is displaced by tumor growth, organ enlargement, or intraperitoneal fluid accumulation. Furthermore, the reference weight of a healthy mouse will vary according to sex, age, body frame size, and in females, pregnancy status. Scoring body condition (BC) by observing the amount of flesh covering bony protuberances is largely independent of the aforementioned confounding variables. The technique of BC scoring as a method for evaluating animal condition and nutritional state has already been validated for use in dairy cows (7–9), beef cows (10), goats (11), sheep (12), and horses (13). In cows, BC score correlates with the amount of subcutaneous fat stores (7, 10) and nutritional status (14). Additionally, abnormal loss of BC was found to be an indicator of mastitis in dairy cows (15). Our goals were to evaluate the accuracy of the BC scoring technique in assessing the health of mice that have organ enlargement concurrent with declining health; compare the accuracy of this method with that of using BW for assessing health status in these animals; and determine the interobserver reliability of the BC scoring technique. P-and E-Selectin double deficient (P/E-/-) mice were chosen for this study because they are susceptible to opportunistic bacterial infections and as their health status declines, their salivary glands, mandibular …