Proposals to split the Ninth Circuit Court of Appeals have been before Congress for decades. Proponents of a split generally argue that the current Ninth Circuit is overburdened, and that creating two or more new circuits with reduced geography, population, and caseloads would improve judicial administration. Opponents of a split reject those claims, saying that the current Ninth Circuit functions well and that the court is a model of innovation. Opponents of a split also suggest that efforts to divide the circuit represent an attack on judicial independence, a claim supporters of a split deny. Efforts to split the Ninth Circuit appeared to be bolstered on November 18, 2005, when the House of Representatives passed the Deficit Reduction Act of 2005 (H.R. 4241), which, among many other provisions, contained language splitting the current Ninth Circuit into a new Ninth Circuit and a Twelfth Circuit. During December 2005 House-Senate conference negotiations, language splitting the Ninth Circuit was dropped from the budget reconciliation package. However, seven bills (H.R. 211, H.R. 212, H.R. 3125, H.R. 4093, S. 1296, S. 1301, and S. 1845) remain under consideration. Most recently, on February 8, 2006, H.R. 4093 was reported from the House Judiciary Committee and placed on the Union Calendar. This report provides information and analysis on the debate concerning proposals to split the Ninth Circuit. The debate over splitting the Ninth Circuit generally focuses on six areas: (1) geography and population, (2) judgeships and caseloads, (3) how quickly the circuit disposes of cases, (4) cost of splitting the circuit, (5) en banc procedures, and (6) the circuit's rulings. Analysis suggests that splitting the Ninth Circuit would have different effects on each of these six areas. Caseload is particularly prominent in the debate over splitting the Ninth Circuit. Proponents of a split suggest that the current Ninth Circuit's caseload is too high, and that reduced caseloads would improve judicial administration. Opponents of a split disagree, saying that if a split occurred, judges in a new Ninth Circuit would have higher caseloads than their counterparts in proposed Twelfth or Thirteenth Circuits. Analysis of the most recently available estimates suggests that if the current Ninth Circuit had been reorganized in 2005, five of seven bills introduced in the 109th Congress splitting the circuit would have yielded somewhat higher caseloads (based on authorized judgeships) in a new Ninth Circuit than in the current Ninth Circuit during the same time period. Six of the bills would have yielded higher caseloads in a new Ninth Circuit than in proposed Twelfth or Thirteenth Circuits. By contrast, one bill (H.R. 3125) would have yielded a higher caseload in a Twelfth Circuit than a new Ninth Circuit. Other factors -- such as how quickly the circuit disposes of cases and complexity of cases -- could also affect caseload considerations. This report will be updated in the event of significant 109th Congress legislative activity regarding efforts to split the Ninth Circuit.