The efficacy of various sclerotherapeutic agents in the control of acute bleeding, via subserosal injection, was assessed in 10 dogs. Blood flow rate (BFR) from severed gastric serosal vessels (diameter, 1.6 to 2.2 mm) was measured for 3 min (ml/min) for a control group and the agent used. The agents tested were 5 ml of normal saline (NS), 5 ml of 3% hypertonic saline (HS), 5 ml of 1:10,000 epinephrine in NS, 5 ml of 1:10,000 epinephrine/HS, 5 ml of 1:20,000 epinephrine/HS, 2 ml of old thrombin "cocktail" (thrombin, cephapirin + 1% tetradecyl), and 2 ml of fresh thrombin cocktail (total seven). One agent was tested per dog; there were one to two dogs in each subgroup. All of the agents showed significant reduction in BFR (except old thrombin) when compared with BFR of control vessels. The reduction ranged from 30% to more than 75% after 1:10 epinephrine/HS. Complete hemostasis was achieved in up to 47% of vessels using 1:20 epinephrine/HS. Overall, the epinephrine solutions achieved the best results. No systemic effects were observed with the use of any of the agents. Histological studies showed that epinephrine caused mild tissue damage, whereas the cocktail caused significant tissue necrosis. This serosal vessel model permits comparison of the effectiveness of each agent; however, clinical extrapolation to mucosal vessels in a patient and the long-term histological changes are not known.