Peripheral sympathetic responses to septic peritonitis and developing septic shock were studied in conscious rats by measuring plasma catecholamines. Adult male Holtzman rats in the fasted state were subjected to anesthesia for implantation of carotid artery cannulae and were divided into three groups: (1) controls with cannulation only, (2) abdominal laparotomy control, and (3) cecal ligation and puncture (CLP) following cannulation. Arterial plasma levels of epinephrine were significantly (P less than .05) elevated at 5 h post-CLP whereas elevations at 16, 20, 24 and 41 h post-CLP were not significant. Plasma NE levels were significantly (P less than .05) elevated at 5, 16, 20, 24 and 41 h post-CLP. Adrenal medullary content of E was not different from control at 20 h following CLP, suggesting that adrenomedullary depletion could not account for low levels of plasma E during developing septic shock. Heart rate was significantly elevated (P less than .05) at 20 h post-CLP and was attenuated by (cardioselective) beta blockade. Mean blood pressure was not altered by CLP treatment. These findings are consistent with the interpretation that there are elevations in local nerve-stimulated release of NE in peripheral tissues during septic peritonitis.