This paper provides a brief and selective review of recent work concerning the alterations in thermoregulation, cardiovascular, and respiratory physiology that occur as a function of different states of sleep and wakefulness. These state‐dependent changes in physiology were once regarded as a source of unwanted variance to be surgically or pharmacologically eliminated. The research paradigm championed by the work described here, however, requires that the endogenously generated state changes be recognized as potent independent variables influencing physiological control systems. Much evidence suggests that central monoamine‐containing neurons mediate many of the state‐dependent changes in thermoregulatory and cardiopulmonary physiology. A general conclusion emerging from these data is that studies of state‐dependent physiology are not merely descriptive; they are essential for a complete characterization of the cellular and molecular mechanisms underlying regulatory physiology.—Lydic, R. State‐dependent aspects of regulatory physiology.FASEB J.1: 6‐15; 1987.