A movie treatment is a narrative, written in the present tense, of a movie idea. It’s used to follow up a ‘pitch’ or synopsis of a story, so that producers can get a clearer look at how you intend to develop your idea. Treatments come in various lengths, depending on the purpose. Short treatments include story beats without a lot of detail. Longer treatments can give your reader a very complete, detailed idea of how your movie will play out from beginning to end.
If you are trying to get the attention of an agent or producer, then you want something relatively short, say 1-2 pages single spaced.
If you already have someone’s attention because they liked your pitch, then you can write something longer and more detailed, say 3-4 single spaced pages.
If you want to lay out the entire movie so that when the reader is finished she or he has a very good idea of exactly what you have in mind, then I find that 6-7 single spaced pages will work.
You can read samples of short, mid-length and long treatments on my Treatments Page .