Aside from Philip St. Ives, the following characters appear in more than one novel:
- Cyril (called "Mac") McCorkle, pub owner in Bonn and Washington, DC, and his business partner/friend Michael Padillo, spy, are in The Cold War Swap, Cast a Yellow Shadow, The Backup Men, and Twilight at Mac's Place.
- Artie Wu and Quincy Durant, con men/adventurers, and their associate Otherguy Overby are in Chinaman's Chance, Out on the Rim, Voodoo, Ltd. Booth Stallings, expert on terrorism, and Georgia Blue, cashiered Secret Service agent, join them in the latter two.
- Howard Mott, a Washington Lawyer, has cameo roles or is mentioned in several novels.
- Ione Gamble, an actress, is a central character in "Voodoo, Ltd." and is mentioned in "Ah, Treachery!".
- Draper Haere, political rainmaker, is a central character in Missionary Stew and is mentioned in Ah, Treachery.
- Minor Jackson and Nicolae Ploscaru, central characters in The Eighth Dwarf, are mentioned in Ah, Treachery.