The set used for Professor Moriarty's hide out was used as a pub/bar in Sherlock Holmes and the Voice of Terror (1942).

The lines that Holmes quotes at the end of the film are a condensed version of William Shakespeare's lines from Richard II. [Richard II, 2.1, 40-51]

One of several titles in the Sherlock Holmes series whose original copyrights were apparently not renewed and have thereby fallen into public domain; as a result, seriously inferior copies are presently being offered by a number of VHS and DVD dealers who do not have access to original studio masters.

Lionel Atwill, who plays Professor Moriarty in the film, earlier played James Mortimer in The Hound of the Baskervilles (1939).

Although credited as an adaptation of Sir Arthur Conan Doyle's short story "The Adventure of the Dancing Men", the plot is an original story based on historical events which happened after Doyle's death. The only resemblance to the credited story is a cameo by the "secret code" of stick figure drawings. There is another moment taken from Doyle's "Sign of Four": the trail of luminous paint is confused when luminous paint is picked up by wheels of another vehicle at a crossroads.

This was the first of Universal's Sherlock Holmes series in which Dennis Hoey appeared as Inspector Lestrade of Scotland Yard.

The fourth of fourteen films based on Arthur Conan Doyle's fictional consulting detective Sherlock Holmes starring Basil Rathbone as Sherlock Holmes and Nigel Bruce as Doctor Watson.

Moriarty taunts Holmes by saying "The needle to the last, eh, Holmes?" Possibly a reference to Sherlock's cocaine habit, an important character element from the books. This could not be depicted openly in this series, due to film taboos of the time. Or maybe this line simply means that Holmes is a "needle" in Moriarty's side.

This was the second Sherlock Holmes feature to be produced at Universal. It was the first to be directed by Roy William Neill.

A modern source lists Philip Van Zandt as Kurt and includes Henry Daniell in the cast as well. However, the role of Kurt is played by Harry Woods and neither Van Zandt nor Daniell appear in the film at all. The unidentified actor mistaken for Daniell plays a Scotland Yard detective slowly driving the police vehicle following the trail of paint, toward the climax of the film. First seen in 3/4 profile leaning out the car window, he does seem to resemble Daniell. However, when he speaks the accompanying line "they fade out again sir" to Dennis Hoey (Insp. Lestrade), and subsequent lines, he clearly has a rather heavy *Brooklyn* accent, and seen in other shots during the scene does not in any way resemble Daniell, and the momentary appearance to the contrary is clearly an optical illusion.

During the sequence showing the trials of the new bomb-sight, several different types of aircraft are seen in the stock footage used. A Douglas A-20 (known in RAF service as the "Boston") takes off, then a Bristol Blenheim flies low past the camera, and finally a Vickers Wellington is seen for the rest of the sequence. The interior of the aircraft shown also appears to be a Wellington, recognisable by its unique framework of aluminium triangles.

In 2018, the UK film channel "Film 4", showed a version of this film, and at least one other 1940s Universal Rathbone Sherlock film, with a modern end card "NBC Universal Television Distribution". This would make sense, as although the film would be (out of copyright) public domain in the USA, in a large portion of the world the film would still be in active copyright to Universal Pictures. Besides which, as its a Universal Picture, they would have access to their own highest available quality masters.

One of the principal actors in this classic Sherlock Holmes film, the man who plays Sir Reginald Bailey, is actually named "Holmes" --- Holmes Herbert. Herbert also starred in several of the other S.H. films in the Basil Rathbone/Nigel Bruce series.

Some of the actors playing "minor" characters use stage theatrical "ethnic" accents which are quite clearly not their own. The accents are probably meant to be UK English, or the country the character is meant to be from, but end up sounding like spies attempting an accent they clearly can't master, unlike Sherlock Holmes' character accents. This gives the story an edge of more potential suspect criminals than there actually is.

Even though Lionel Atwill is cast as the main villain, it actually takes him quite a while to enter the film properly.

By the time this film was released in 1942, Lionel Atwill's career was in rapid decline.