Over thirty actors auditioned for the lead role, with William Shatner the eventual winner, though he then declined it. James Franciscus was also offered the role, but had committed himself to another (eventually unmade) series at the time.
The building they used for the overall shot of Blair General Hospital is a matte shot based on the Los Angeles County General Hospital. The Thalberg Building on the MGM lot was used for closer shots of the stairs and doorways of the hospital.
The establishing shots of Blair General Hospital in the series are from the first Dr. Kildare movie, Young Dr. Kildare (1938).
An episode titled "The Eleventh Hour", with guest stars Wendell Corey and Vera Miles, was filmed in 1961 and intended to be shown during the first season of "Dr. Kildare". The episode as originally filmed never aired as part of the "Kildare" series; it was instead revised, eliminating all "Kildare" references, and was eventually broadcast on October 3, 1962 as the pilot episode of the series "The Eleventh Hour." The original unaired Kildare episode was included in the 2013 DVD release of the show's first season.
Spoofed in Mad Magazine as "Dr. Kiljoy".