Polyjuice Potion transforms one's appearance into that of someone else for exactly an hour, per dose. If it is taken repeatedly, the transformation can be maintained over time.
 Second Book
Hermione Granger thinks of using this potion to spy on Draco Malfoy to try and find out if he is the heir of Slytherin after she hears Severus Snape talk about it in Potions class. Hermione plans to make the potion by looking up the recipe in a book called Moste Potente Potions which is kept in the restricted section of the Hogwarts library. Hermione asks Professor Lockhart to sign a permission form so she can check out the book from the library. The trio then secretly brews the potion in Moaning Mrytle's bathroom, using some ingredients from the students' cupboard, and some stolen from Professor Snape's private stores. Harry Potter uses the potion to look like Goyle, and Ron Weasley uses the potion to impersonate Crabbe. Hermione plans to use the potion to look like Millicent Bulstrode, but accidentally uses a cat hair, thinking it was Millicent's. Hermione ends up with a cat face and in the hospital wing. The potion is not supposed to be used for animal transformations.
 Fourth Book
Barty Crouch Jr. takes Polyjuice Potion throughout the whole school year in order to impersonate Alastor (Mad-Eye) Moody. This is part of a plot to create a new body for Lord Voldemort with the use of Harry Potter's blood.
 Fifth Book
While taking his O.W.L. exams during his fifth year, Harry Potter is asked to write an accurate description of the effects of Polyjuice Potion on the person who drinks the potion. He is able to answer the question easily, having taken the potion himself during his second year, when Harry and Ron temporarily became Crabbe and Goyle.
 Sixth Book
Polyjuice Potion is featured in the Ministry of Magic pamphlets. Wizards are advised to agree on security questions to try to detect Death Eaters that are using Polyjuice Potion to masquerade as others. Polyjuice Potion is also one of the potions Professor Horace Slughorn quizzes the students on in his first Potions lesson. Hermione Granger correctly identifies the potion, and Harry Potter reminisces about how she brewed it in their second year.
 Seventh Book
Polyjuice Potion is used to create seven Potters to confuse the Death Eaters while trying to move the real Harry Potter to a safe house. Remus Lupin indicates that the potion cannot be used for any non-human transformation. The trio also used Polyjuice Potion throughout the book to disguise themselves and break into the <Ministry of Magic and Gringotts. Can only be taken by complete humans. As we learn after the seven potters chapter. When Lupin make sure that Harry is actually Harry and not an impostor and doesn't ask Hagrid a question because half humans can't take the potion.
 Making the Potion
Polyjuice Potion is made with lacewing flies, leeches, fluxweed, knotgrass, powdered horn of a bicorn, shredded skin of a boomslang, and a bit of whoever one wants to change into. The fluxweed needs to be picked at the full moon and the lacewings have got to be stewed for twenty-one days so the potion takes about a month to prepare.
The Polyjuice Potion is first described as looking like "thick, dark mud, bubbling sluggishly". When Harry is officially taught about the potion by Horace Slughorn, he again describes it as a "slow-bubbling, mudlike substance".  The potion changes color once the bit of the person one wishes to change into is added. When Harry's hair was added to the potion it began to froth and smoke, then, all at once, turn a clear, bright gold. Hermione Granger notes that Harry looks "much tastier than Crabbe and Goyle".  Goyle's potion turned the khaki color of a booger and Crabbe's potion was a dark, murky brown. The cat hair Hermione believes to be a hair from Millicent Bulstrode turns the potion a sick sort of yellow.