This monograph discusses the current treatment of spasticity via intrathecal baclofen (ITB) therapy. It describes the pathophysiology and the primary anatomic substrate of spasticity, and the current modern surgical and pharmacologic treatment options. Baclofen pumps are discussed in detail, including their implantation procedure, and basic modes of operation and design. Complications of ITB treatment are examined including infection, pump failure, and baclofen overdosing and withdrawal issues. Results from a recent cost-analysis study of ITB therapy are included, and promising future trends in the treatment of spasticity.