According to testimony from Aladena Fratianno, (Jimmy the Weasel), a Mafia boss-turned-FBI informant, the Chicago family of the Mafia ordered the assassination of producer Desi Arnaz, because they didn't like (a) the fact that the success of the show was focusing attention on the Mafia and (b) the show's portrayal of Italians. Fratianno said that two hitmen hid themselves near Arnaz's house one night waiting for him to show up, but he never did. Shortly afterwards, the assassination order was rescinded when it was realized that Arnaz's murder would cause the Mafia more trouble than it was worth.
Walter Winchell received a reported $25,000 per episode for his narration on this series. With his signature machine gun dialogue delivery, he could apparently rack up almost 200 words per minute.
Robert Stack (Eliot Ness) and Walter Winchell (Narrator) are the only actors to appear in all 119 episodes of the series.
Van Heflin and Van Johnson turned down the role of Eliot Ness. Fred MacMurray, Jack Lord, and Cliff Robertson were also considered for the part.
To counter some of the claims that the show was anti-Italian, later episodes gave a more prominent role to Agent Enrico Rossi (the Italian-American member of Ness' team) in order to show an Italian-American as a hero working for law and order. Rossi was played by Nicholas Georgiade, who was Greek.