And the pot dispensaries in Colorado are hopping.
Four-20 is doper slang for smoking weed and April 20, or 4/20, is the unofficial pot holiday.
People who work in medical marijuana dispensaries say it's like Halloween week at a costume shop.
In Boulder, the Dr. Reefer dispensary has hired extra workers.
There will be a smoke-out in Boulder at the University of Colorado campus.
The event drew 10,000 people last year.
Despite warnings from school officials, more are expected this 4/20.
While the university bans pot smoking on campus, few citations are issued.
