Physiological responses of multiple systems (e.g. endocrine, immune, autonomic) are key for determining how animals respond to their environment. Understanding how multiple physiological mechanisms function together provides further insight into how individuals function. The objective of this study was to determine if there are reliable relationships among different physiological systems within an individual. We measured several physiological responses within the same individuals and used correlational analysis to identify related processes. We measured hormonal stress response, innate and adaptive immune function, and sympathetic reactivity in 54 adult male Sprague-Dawley rats. To measure hormonal stress responses, we conducted an acute restraint test and measured glucocorticoid (GC) responses. Innate immunity and basal GCs were measured during an 8-hour period after lipopolysaccharide injection. Adaptive immunity was measured with relative hind foot swelling after keyhole limpet hemocyanin (KLH) re-exposure. And heart rate was measured non-invasively during an acute restraint stress to determine fluctuations in sympathetic activity. We found that GCs were associated with most other physiological measures; specifically, elevated GCs during the innate immune challenge were associated with elevated pro-inflammatory cytokine responses (TNF-alpha and IL-6). Additionally, elevated cell-mediated immune responses were associated with elevated circulating GCs during KLH exposure and elevated circulating TNF-alpha levels during the innate immune challenge. Heart rate in response to restraint was not associated with any physiological measures. These results are the first step in understanding how different physiological systems interact to support organismal responses to complex environmental challenges.