Most researchers use butterfly needles to administer fluids via the tail vein. We now carry a system developed that will allow easier access for both timed injections and repeated bolus adminis-tration. The MTV-1 system incorporates a small catheter that is easily inserted into the tail vein and will remain insitu in a restrained mouse for as long as restrain is feasible. Due to the flexibility and size of the catheter, trauma to the tail vein is minimized, allowing for long term and repeated bolus dosing. By avoiding the damage associated with indwelling needles there is an increased chance that the tail vein will remain viable for the duration of the study.