For studying the role of cachectin (Tumor Necrosis Factor -TNF) in septic shock we have developed a physiological monitoring system for laboratory rats. Temperature and direct arterial pressure were monitored. Special carotid/aortic catheters were designed and tested for frequency response. During actual studies septic shock was induced and physiologically characterized. Preliminary results show that findings based on assayed values of TNF are inconclusive and that additional approaches may be warranted.