Elsa's shimmering ice blue gown is by some margin the most popular costume for 2014, out-selling Anna's bodice and skirt by two to one.
For boys, the emphasis is on superheroes; Spider Man is the top costume, and five more superheroes appear in the top 10.
The number two most popular costume for boys in the U.S.is a Ninja, followed by Batman, Superman and Captain America.
The figures come from the e-commerce site Zulily, which revealed that after the Frozen girls, witch costumes come in third place, while mermaids and pirates are fourth and fifth most popular.
And other princesses from classic movies and fairy tales also have enduring popularity: Snow White is the seventh most popular pick, and Cinderella comes in at number 10.
Boys may be fond of their superheroes, but there's one villain that is a perennial favourite and made the list yet again this year: Darth Vader from Star Wars.
Amy Goodman, lifestyle editor for Zulily, said the key to enjoying Halloween was to plan ahead.
She said: "A head start on Halloween prep allows you to save on the stuff you really want rather than settling for the last costumes in the sales bin, and gives you time to make your own décor with DIY Halloween projects."
TOP 10 GIRLS' HALLOWEEN COSTUMES
1. Elsa (Frozen)
2. Anna (Frozen)
7. Snow White
8. Wonder Woman
9. 50s-Style Poodle Dress
TOP 10 BOYS' HALLOWEEN COSTUMES
1. Spider Man
5. Captain America
7. Optimus Prime
8. Darth Vader
9. Iron Man
10. Red Ranger
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