Otto Brower and Osa Johnson followed Stanley's path through Kenya, Tanganyika and Uganda with their crew and returned with 100,000 feet of film for use in the safari sequences.
Neither Spencer Tracy nor Walter Brennan ever actually went to Africa during the making of this film. Stand-ins for both of them were used in the long shots during the safari sequences, and whenever Tracy or Brennan were shown "on safari" in close-up against African scenery, they were acting in front of a rear projection screen.
The movie was dubbed into Spanish, Portuguese and Dutch.