The pilot film for the long-run series introduced the kindly small-town general practitioner who, following a mild coronary, grudgingly brings in an independent, motorcycling young associate to help share his workload. Welby's lady friend and his family, part of the plot of this movie, were written out of the subsequent series, with only his medical sidekick, Steven Kiley, and their secretary/nurse, Consuelo, remaining as regulars.
| Actor | Role |
|---|---|
 Robert YoungMarcus Welby | Marcus Welby |
 James BrolinSteven Kiley | Steven Kiley |
 Anne BaxterMyra Sherwood | Myra Sherwood |
 Susan StrasbergTina Sawyer | Tina Sawyer |
 Lew AyresDr. Andrew Swanson | Dr. Andrew Swanson |
 Tom BosleyTiny Baker | Tiny Baker |
 Pete DuelLew Sawyer | Lew Sawyer |
 Sheila LarkenSandy Welby | Sandy Welby |
| MMercer HarrisRay Wells | Ray Wells |
| PPenny SantonConsuelo Guadalupe-Lopez | Consuelo Guadalupe-Lopez |
 Richard LooKenji Yamashita | Kenji Yamashita |
 Larry LinvilleNot listed | Not listed |
 Ben WrightNot listed | Not listed |
| RRon StokesNot listed | Not listed |
 Allison McKayNot listed | Not listed |
| CCraig LittlerNot listed | Not listed |
| SSheila RogersNot listed | Not listed |
 Fran RyanNot listed | Not listed |