The authors sought to determine whether endogenous splenic tissue placed in a subcutaneous pouch ("spleen-o-port") could function as a viable alternative to central venous catheters/ports for long-term venous access. A small transverse incision was made in the left upper quadrant of each puppy (n = 6) under general anesthesia. Using a stapler, the authors divided the splenic parenchyma. The superior portion was returned to its native location, and a subcutaneous pocket was created to house the inferior pole with its attached vascular supply. The fascial and muscular layers were closed with care to avoid compressing the blood supply to the spleen-o-port. Postoperatively the dogs resumed normal activity. There have been no deaths, infectious complications, splenic ruptures, or thromboses over a 6-month period. Under fluoroscopy, the dogs were imaged from postoperative day (POD) 10 to 177. Contrast agent entering the splenic parenchyma was promptly visualized in the splenic vein and then filled the portal vein. Electrolyte measurements from spleen-o-port blood samples were identical to those from peripheral venous samples. After gentamicin (mixed in a crystalloid solution) was infused through the spleen-o-port, the peak serum level corresponded to the therapeutic levels observed after standard intravenous administration. The spleen-o-port permits rapid infusion of drugs and crystalloid, and allows repetitive blood sampling while eliminating the foreign body that can promote septicemia in the immunocompromised patient.