Infusion of experimental compounds into the vascular system of rodents and the need to collect blood and other biological fluids from small animals comprise an area of emerging importance to biomedical research and drug discovery and development. The advances in the development of transgenic rodents coupled with technical progress in the manufacture and commercial availability of various catheters, swivels, tethers, infusion pumps, and sample collection systems that are described have enabled biomedical scientists to miniaturize vascular infusion and sample collection systems previously used in animal species larger than the rat or mouse. Use of these advanced, miniature vascular infusion systems in rodents is possible only when careful planning of experimental design, expert surgical technique, adequate postoperative care, and fundamental animal welfare considerations are meticulously taken into consideration. Use of these vascular infusion systems in rodents promotes animal welfare and scientific progress through the reduction and refinement of animal models.