The spinal cord represents a complex system that serves in the encoding of sensory information and organization of autonomic and somatomotor outflow. As such, it has become a target of investigation for subjects ranging from pain to hypertension to motor spasticity. A primary method in such investigations is the specific delivery of drugs into the spinal intrathecal space to assess such agents with the actions limited to the spinal cord. The rat has served as a primary model in these investigations. It provides for the ability to deliver such agents both acutely and chronically in the absence of anesthesia or restraint. These goals can be accomplished by the placement of intrathecal catheters in the spinal space. This model, first demonstrating the feasibility of routinely catheterizing the lumbar intrathecal space in 1976, led directly to enabling a large number of studies focusing on spinal drug actions. As a test model, it has provided for the acquisition of an exceptional amount of information on the pharmacological and physiological mechanisms of spinal function, drug screening, drug efficacy and safety studies, and pharmacokinteics of spinally delivered drugs. The modified surgical method of intrathecal catheter placement, microinjection drug delivery, and behavioral parameters are described in detail.