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.

(As of Jan. 9, 2007)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

30. Joe Lieberman (ID-Conn.), Jan. 3, 1989

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

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

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

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

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

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

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

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

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

40. Kay Bailey Hutchison (R-Texas),

June 14, 1993

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

70. Hillary Rodham Clinton (D-N.Y.),

Jan. 3, 2001

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

90. Bob Menendez (D-N.J.), Jan. 18, 2006

91. Benjamin Cardin (D-Md.), Jan. 4, 2007

92. Bernie Sanders (I-Vt.), Jan. 4, 2007

93. Sherrod Brown (D-Ohio), Jan. 4, 2007

94. Jim Webb (D-Va.), Jan. 4, 2007

95. Bob Casey (D-Pa.), Jan. 4, 2007

96. Bob Corker (R-Tenn.), Jan. 4, 2007

97. Claire McCaskill (D-Mo.), Jan. 4, 2007

98. Amy Klobuchar (D-Minn.), Jan. 4, 2007

99. Sheldon Whitehouse (D-R.I.), Jan. 4, 2007

100. Jon Tester (D-Mont.), Jan. 4, 2007