Sickness behavior has become a common expression in the description of general symptoms of diseases and regarded as partly or fully advantageous for the patient to combat infection or other disturbance acting on the body. Several components of sickness behavior such as anorexia, sleepiness and inactivity have significant energetic connotations and hence may affect body mass and/or body temperature. Thermoregulatory accompaniments of sickness behavior could be either fever or hypothermia depending on the nature and severity of disease. A survey of the relevant literature has identified afferent, central and efferent mechanisms that may allow separate or coordinated appearance of behavioral and/or thermoregulatory aspects of these symptoms occurring under different experimental conditions. An attempt has been made to find some biological logic in the appearance of various components of sickness behavior and changes in body temperature that could explain the purported positive value of sickness behavior in disease survival.