The effect of short-term treatment with aspirin or dextran on the patency of bovine heterografts in the venous system was investigated. Animals treated preoperatively and for three days postoperatively with either aspirin (600 mgm BID) or low molecular weight dextran (500 cc/day) had statistically significant increased graft patency as compared to controls during the treatment interval. Significance was lost, however, after cessation of therapy. These results suggest that either aspirin or low molecular weight dextran would be useful adjuvants to venous reconstruction. If used in the venous system, bovine heterografts might be expected to yield better short term patency with adjuvant therapy employing either dextran or aspirin.