Methods were developed for the insertion and maintenance of long-term central venous catheters in dogs in order to provide reliable venous access during bone marrow transplantation. Single-lumen, 9.6 Fr Hickman catheters with a VitaCuff were used. The catheter was inserted into the jugular vein via a surgical cut-down, and tunnelled subcutaneously to exit over the thoracic spine. Fluoroscopic guidance was necessary to ensure proper positioning of the catheter tip in the right atrium. The catheter was secured at the venous entrance site with a grommet and at the cutaneous exit site with a finger-cuff suture. The exit site was bandaged; dressings were changed daily. Five dogs were studied. Catheter insertion and maintenance techniques were developed using two dogs. For the other three dogs, which developed 7 wk of profound myelosuppression induced by total body irradiation, the catheters were used for blood sampling and infusions of antibiotics, fluids, and blood products. For these three dogs there were 261 total catheter-days. Complete catheter obstruction did not occur. Partial obstruction (inability to withdraw blood) occurred for 13 days with one catheter. The tip of this catheter was in the cranial vena cava. One irradiated dog had a staphylococcal exit site infection for several days after catheter insertion, which resolved with antibiotic therapy. Infections of the subcutaneous tunnel, and catheter associated bacteremia, were not identified. Infectious and hemorrhagic complications of myelosuppression were less severe than in six other dogs where intermittent venipuncture was used for vascular access during radiation induced myelosuppression. In conclusion, long-term central venous catheterization is feasible in dogs during profound myelosuppression and markedly facilitates patient management.