Arginine vasopressin (AVP) is used to treat esophageal variceal hemorrhage but has the drawbacks of rebleeding and reported coronary insufficiencies. In conscious dogs (n = 23) we compared AVP and an analog, triglycyl desamino lysine vasopressin (TDLVP), for arterial pressor responses and changes in regional blood flow. Dogs were infused with saline (n = 5), AVP (n = 7) or TDLVP (n = 7), and blood flow was measured with microspheres during control, infusion and postinfusion in 46 tissue sections including pieces of the esophagus, stomach, liver, kidney, spleen, heart, skin, muscle and brain. TDLVP (1.0 micrograms/kg/min) and AVP (0.025 micrograms/kg/min) produced a similar mean arterial pressure increase of 23 mm Hg and a heart rate decrease of 38 beats/min. TDLVP sustained the increase in mean arterial pressure and reduction in heart rate at 30 min postinfusion whereas AVP did not. Neither AVP nor TDLVP showed a reduction in brain, kidney or liver flow; however, both produced reductions (73 and 61%, respectively, P less than .01) in mucosal-esophageal flow. Only TDLVP reduced mucosal-fundus blood flow (P less than .01). Endocardial flow was reduced (27%) in both TDLVP and AVP groups; however, heart rate also decreased during this time and a linear correlation between these two measurements yielded a value for r2 of 0.83. Thus, TDLVP offers a therapeutic alternative to AVP in treating gastroesophageal varices due to its longer duration of action as represented by the sustained reduction in esophageal and mucosal-fundus flow.