Both actors who played Amos and Andy were white in what was known as "blackface" makeup at the time. Blackface had been mostly abandoned by mainstream American films by 1930, unless it was diegetic (i.e. characters are performers who wear blackface as part of their act). It was decided that all African-American speaking roles in this film would, for aesthetic continuity, be played by white actors in blackface; the only exceptions were Duke Ellington and his orchestra appearing in the party scene, and the occasional non-speaking extra in scenes set in Harlem.
Although Bing Crosby, Harry Barris and Al Rinker, as The Rhythm Boys, are heard on the soundtrack singing "Three Little Words", three African-American men are seen on the screen, supposedly doing the vocalizing, with megaphones disguising their lip movements so that there would not be a synchronization problem.
Based on the extremely popular radio show, this reportedly became RKO's biggest hit until King Kong (1933).
This huge box-office hit would have normally guaranteed a sequel or even a series. However, creators Freeman F. Gosden and Charles J. Correll were not happy with this feature film version. This resulted in no more Amos 'n Andy films being made. Four years later. Gosden and Correll did lend their voices to a pair of animated Amos 'n Andy shorts produced by the Van Beuren Studios, which were also distributed by RKO.