Rankings are based on the date the oath of office was taken, except in cases when a Senator resigns after the election and the winner of the election is appointed to fill the remainder of the term. For Senators sworn in on the same date, seniority is determined by prior Senate service, followed by vice presidential, House, Cabinet and gubernatorial service, according to the Senate Rules and Administration Committee. If ties remain, seniority is based first on state population and then alphabetically, if there are two Senators from the same state. The panel provided the ranking information but as a matter of committee policy would not confirm the list.

1. Robert Byrd (D-W.Va.), Jan. 7, 1959

2. Edward Kennedy (D-Mass.), Nov. 7, 1962

3. Daniel Inouye (D-Hawaii), Jan. 9, 1963

4. Ted Stevens (R-Alaska), Dec. 24, 1968

5. Pete Domenici (R-N.M.), Jan. 3, 1973

6. Joseph Biden (D-Del.), Jan. 3, 1973

7. Patrick Leahy (D-Vt.), Jan. 3, 1975

8. Paul Sarbanes (D-Md.), Jan. 3, 1977

9. Dick Lugar (R-Ind.), Jan. 3, 1977

10. Orrin Hatch (R-Utah), Jan. 3, 1977

11. Max Baucus (D-Mont.), Dec. 15, 1978

12. Thad Cochran (R-Miss.), Dec. 27, 1978

13. John Warner (R-Va.), Jan. 3, 1979

14. Carl Levin (D-Mich.), Jan. 3, 1979

15. Chris Dodd (D-Conn.), Jan. 3, 1981

16. Chuck Grassley (R-Iowa), Jan. 3, 1981

17. Arlen Specter (R-Pa.), Jan. 3, 1981

18. Jeff Bingaman (D-N.M.), Jan. 3, 1983

19. John Kerry (D-Mass.), Jan. 2, 1985

20. Tom Harkin (D-Iowa), Jan. 3, 1985

21. Mitch McConnell (R-Ky.), Jan. 3, 1985

22. Jay Rockefeller (D-W.Va.), Jan. 15, 1985

23. Barbara Mikulski (D-Md.), Jan. 6, 1987

24. Richard Shelby (R-Ala.), Jan. 6, 1987

25. John McCain (R-Ariz.), Jan. 6, 1987

26. Harry Reid (D-Nev.), Jan. 6, 1987

27. Kit Bond (R-Mo.), Jan. 6, 1987

28. Kent Conrad (D-N.D.), Jan. 6, 1987

29. Trent Lott (R-Miss.), Jan. 3, 1989

30. James Jeffords (I-Vt.), Jan. 3, 1989

31. Conrad Burns (R-Mont.), Jan. 3, 1989

32. Herb Kohl (D-Wis.), Jan. 3, 1989

33. Joe Lieberman (D-Conn.), Jan. 3, 1989

34. Daniel Akaka (D-Hawaii), April 28, 1990

35. Larry Craig (R-Idaho), Jan. 3, 1991

36. Dianne Feinstein (D-Calif.), Nov. 10, 1992

37. Byron Dorgan (D-N.D.), Dec. 15, 1992

38. Barbara Boxer (D-Calif.), Jan. 5, 1993

39. Judd Gregg (R-N.H.), Jan. 5, 1993

40. Russ Feingold (D-Wis.), Jan. 5, 1993

41. Patty Murray (D-Wash.), Jan. 5, 1993

42. Bob Bennett (R-Utah), Jan. 5, 1993

43. Kay Bailey Hutchison (R-Texas), June 14, 1993

44. James Inhofe (R-Okla.), Nov. 30, 1994

45. Olympia Snowe (R-Maine), Jan. 4, 1995

46. Mike DeWine (R-Ohio), Jan. 4, 1995

47. Jon Kyl (R-Ariz.), Jan. 4, 1995

48. Craig Thomas (R-Wyo.), Jan. 4, 1995

49. Rick Santorum (R-Pa.), Jan. 4, 1995

50. Bill Frist (R-Tenn.), Jan. 4, 1995

51. Ron Wyden (D-Ore.), Feb. 6, 1996

52. Sam Brownback (R-Kan.), Nov. 27, 1996

53. Pat Roberts (R-Kan.), Jan. 7, 1997

54. Dick Durbin (D-Ill.), Jan. 3, 1997

55. Tim Johnson (D-S.D.), Jan. 3, 1997

56. Wayne Allard (R-Colo.), Jan. 3, 1997

57. Jack Reed (D-R.I.), Jan. 3, 1997

58. Mary Landrieu (D-La.), Jan. 3, 1997

59. Jeff Sessions (R-Ala.), Jan. 3, 1997

60. Gordon Smith (R-Ore.), Jan. 3, 1997

61. Chuck Hagel (R-Neb.), Jan. 3, 1997

62. Susan Collins (R-Maine), Jan. 3, 1997

63. Mike Enzi (R-Wyo.), Jan. 3, 1997

64. Charles Schumer (D-N.Y.), Jan. 3, 1999

65. Jim Bunning (R-Ky.), Jan. 3, 1999

66. Mike Crapo (R-Idaho), Jan. 3, 1999

67. Blanche Lincoln (D-Ark.), Jan. 3, 1999

68. Evan Bayh (D-Ind.), Jan. 3, 1999

69. George Voinovich (R-Ohio), Jan. 3, 1999

70. Lincoln Chafee (R-R.I.), Nov. 4, 1999

71. Ben Nelson (D-Neb.), Jan. 3, 2001

72. Tom Carper (D-Del.), Jan. 3, 2001

73. Debbie Stabenow (D-Mich.), Jan. 3, 2001

74. John Ensign (R-Nev.), Jan. 3, 2001

75. Maria Cantwell (D-Wash.), Jan. 3, 2001

76. George Allen (R-Va.), Jan. 3, 2001

77. Bill Nelson (D-Fla.), Jan. 3, 2001

78. Hillary Rodham Clinton (D-N.Y.), Jan. 3, 2001

79. Jon Corzine (D-N.J.), Jan. 3, 2001

80. Mark Dayton (D-Minn.), Jan. 3, 2001

81. Jim Talent (R-Mont.), Nov. 23, 2002

82. Lisa Murkowski (R-Alaska), Dec. 20, 2002

83. Frank Lautenberg (D-N.J.), Jan. 3, 2003

84. Saxby Chambliss (R-Ga.), Jan. 3, 2003

85. Lindsey Graham (R-S.C.), Jan. 3, 2003

86. John Sununu (R-N.H.), Jan. 3, 2003

87. Elizabeth Dole (R-N.C.), Jan. 3, 2003

88. Lamar Alexander (R-Tenn.), Jan. 3, 2003

89. John Cornyn (R-Texas), Jan. 3, 2003

90. Norm Coleman (R-Minn.), Jan. 3, 2003

91. Mark Pryor (D-Ark.), Jan. 3, 2003

92. Richard Burr (R-N.C.), Jan. 4, 2005

93. Johnny Isakson (R-Ga.), Jan. 4, 2005

94. David Vitter (R-La.), Jan. 4, 2005

95. Jim DeMint (R-S.C.), Jan. 4, 2005

96. Tom Coburn (R-Okla.), Jan. 4, 2005

97. John Thune (R-S.D.), Jan. 4, 2005

98. Mel Martinez (R-Fla.), Jan. 4, 2005

99. Barack Obama (D-Ill.), Jan. 4, 2005

100. Ken Salazar (D-Colo.), Jan. 4, 2005