I personally consider it kinda a drama-horror adventure, though by today's definition of horror it's not at all scary or suspenseful (though I guess technically it's, nonetheless, more "horror" than any other genre).

While it can be legitimately considered science-fiction, I don't really think of it as that, since it's not like the monster is a robot or the such (unlike the evil Maria human-like robot in the silent classic Metropolis).

I think of it as science fiction, since Frankenstein is a scientist piecing together parts from corpses to create his monster. It could be classified as either, I suppose.

The novel is considered to be 'science fiction' so I suppose that would also apply to the movie? But it also is in the 'horror' genre.

@A-Dubya said:

I think of it as science fiction, since Frankenstein is a scientist piecing together parts from corpses to create his monster. It could be classified as either, I suppose.

And did you know? The Bride of Frankenstein passes the Bechdel test. ;.)

It’s both and neither. The most fitting category is probably Westerns. It may take place in a castle, but that’s just an allegory for the desolation of the open plains. The monster is the deprivation suffered by settlers. And Dr. Frankenstein is just an alliterative substitution for “Franks and Beans.” I hope that clarifies the issue.

ED: This also raises the possibility that Mel Brooks conceived the movie Young Frankenstein after filming the bean scene in Blazing Saddles.

I say it's a Romantic Fantasy. Sexy sexy Frankenstein.