 | Shaun Cassidy | ... | Joe Hardy (36 episodes, 1977-1978) |
 | Parker Stevenson | ... | Frank Hardy (36 episodes, 1977-1978) |
 | Pamela Sue Martin | ... | Nancy Drew / ... (21 episodes, 1977-1978) |
 | Ed Gilbert | ... | Fenton Hardy (19 episodes, 1977-1978) |
 | William Schallert | ... | Carson Drew (11 episodes, 1977-1978) |
 | Lisa Eilbacher | ... | Callie Shaw (7 episodes, 1977) |
 | Edith Atwater | ... | Aunt Gertrude / ... (7 episodes, 1977) |
 | George O'Hanlon Jr. | ... | Ned Nickerson (7 episodes, 1977) |
 | Jean Rasey | ... | George Fayne (7 episodes, 1977) |
 | Jack Kelly | ... | Harry Hammond (5 episodes, 1978-1979) |
 | Janet Julian | ... | Nancy Drew (4 episodes, 1978) |
 | Robert Karnes | ... | Sheriff King (4 episodes, 1977) |
 | Susan Buckner | ... | George Fayne (3 episodes, 1977-1978) |

| Anne Lockhart | ... | Jess / ... (3 episodes, 1977-1978) |

| Ruth Cox | ... | Bess Marvin (3 episodes, 1977) |
 | Edd Byrnes | ... | Paul Owens / ... (3 episodes, 1978) |

| Eric Lawrence | ... | Vince Carroll / ... (3 episodes, 1978) |
 | Victor Holchak | ... | Agent Thomas / ... (2 episodes, 1977-1978) |
 | Bonnie Ebsen | ... | Madge / ... (2 episodes, 1977) |
 | Herb Voland | ... | Chief Collig (2 episodes, 1977) |
 | Derek Murcott | ... | 1st Mate / ... (2 episodes, 1977-1978) |
 | Walt Davis | ... | Eric Litton / ... (2 episodes, 1977) |
 | Robert Sampson | ... | Keller (2 episodes, 1977-1978) |
 | Pernell Roberts | ... | Detective Superintendant Molly / ... (2 episodes, 1978) |
 | Skip Ward | ... | 2nd Agent / ... (2 episodes, 1977-1978) |
 | Susan Woollen | ... | Cathy / ... (2 episodes, 1977) |
 | Dane Clark | ... | Captain Powers (2 episodes, 1977-1978) |
 | Debra Clinger | ... | Harriet Alexander / ... (2 episodes, 1977-1978) |
 | Gary Springer | ... | Chet / ... (2 episodes, 1977) |
 | Janet Curtis-Larson | ... | Blonde / ... (2 episodes, 1977) |
 | Walter Klenhard | ... | Officer / ... (2 episodes, 1978) |
 | Patch Mackenzie | ... | Charlene / ... (2 episodes, 1977-1978) |
 | Robin Mattson | ... | Carla Bradley / ... (2 episodes, 1977-1978) |
 | Craig Stevens | ... | Alexander Cartel (2 episodes, 1977-1978) |
 | Phillip R. Allen | ... | Everett / ... (2 episodes, 1977) |

| Leon Askin | ... | Haufman Berger (2 episodes, 1977) |

| Val Avery | ... | Skipper / ... (2 episodes, 1977) |
 | Claude Bessy | ... | Frenchie (2 episodes, 1977) |
 | J.D. Cannon | ... | Jason Fox (2 episodes, 1977) |
 | Carl Esmond | ... | Kolbe (2 episodes, 1977) |
 | Lorne Greene | ... | Inspector Hans Stavlin (2 episodes, 1977) |

| Casey Kasem | ... | Paul Hamilton (2 episodes, 1977) |

| Floyd Levine | ... | Brandon (2 episodes, 1977) |
 | Larry Levine | ... | Clerk / ... (2 episodes, 1977) |

| Clyde Lucas | ... | Lead Guitar in Alison Troy Band (Paul Williams Band) (2 episodes, 1977) |
 | Sandie Newton | ... | Mandy (2 episodes, 1977) |
 | Michael Quinn | ... | David Hargrove (2 episodes, 1977) |
 | Clive Revill | ... | Phil Bronson (2 episodes, 1977) |

| Bernie Taupin | ... | Tim Carstairs (2 episodes, 1977) |
 | John Van Dreelen | ... | Mayor (2 episodes, 1977) |
 | James Wainwright | ... | Arlo Weatherly (2 episodes, 1977) |

| Norbert Weisser | ... | Gurd (2 episodes, 1977) |
 | Paul Williams | ... | Allison Troy (2 episodes, 1977) |
 | Michael Botts | | (2 episodes, 1978) |
 | Kevin Brophy | ... | Jocco Halsey (2 episodes, 1978) |
 | James T. Callahan | ... | Haggarty (2 episodes, 1978) |
 | Helena Carroll | ... | Laura Taylor (2 episodes, 1978) |

| Kim Cattrall | ... | Marie Claire (2 episodes, 1978) |

| Linda Dano | ... | Josette (2 episodes, 1978) |
 | Howard Duff | ... | Lt. Martinelle (2 episodes, 1978) |

| Robert Feero | ... | Kellgyn (2 episodes, 1978) |
 | Peter Forster | ... | Desk Clerk (2 episodes, 1978) |
 | Pamela Franklin | ... | Marla (2 episodes, 1978) |
 | Hal Frederick | ... | Mabotu / ... (2 episodes, 1978) |
 | David Gates | ... | Himself (2 episodes, 1978) |
 | Julius Harris | ... | Mr. Dove (2 episodes, 1978) |
 | Vince Howard | ... | Lieutenant / ... (2 episodes, 1978) |
 | Larry Knechtel | | (2 episodes, 1978) |

| Ray Milland | ... | Dr. Orin Thatcher (2 episodes, 1978) |

| Nehemiah Persoff | ... | Vladimir (2 episodes, 1978) |
 | Angelo Rossitto | ... | Hawker (2 episodes, 1978) |
 | Johnny Sekka | | (2 episodes, 1978) |
 | Kevin Tighe | ... | Steve (2 episodes, 1978) |
 | Bobby Van | | (2 episodes, 1978) |
|
| Joyce Heft Brotman | .... | co-producer / producer (33 episodes, 1977-1979) |
| Glen A. Larson | .... | executive producer (33 episodes, 1977-1979) |
| Arlene Sidaris | .... | co-producer / producer (33 episodes, 1977-1979) |
| Andrew Mirisch | .... | associate producer (20 episodes, 1977-1979) |
| Michael Sloan | .... | supervising producer (17 episodes, 1977-1978) |
| B.W. Sandefur | .... | producer / supervising producer (11 episodes, 1977) |
| Joe Boston | .... | producer (10 episodes, 1977-1978) |
| Christopher Crowe | .... | producer (10 episodes, 1978-1979) |
| Ben Kadish | .... | producer (10 episodes, 1978-1979) |
| Gilbert Bettman Jr. | .... | associate producer (9 episodes, 1977-1978) |
| Winrich Kolbe | .... | associate producer (6 episodes, 1977) |
| Lou Shaw | .... | producer (3 episodes, 1977) |
| |