A leaked email - allegedly sent to the likes of Alicia Keys, Carrie Underwood and Miranda Lambert by broadcaster CBS - bans "problematic" outfits exposing "female breasts", "buttock crack" and "the genital region" at Sunday's (February 10) ceremony at the Los Angeles Staples Centre.
According to Deadline, the reminder reads: "Please be sure that buttocks and female breasts are adequately covered. Thong-type costumes are problematic.
"Please avoid exposing bare fleshy under curves of the buttocks and buttock crack.Bare sides or under curvature of the breasts is also problematic. Please avoid sheer see-through clothing that could possibly expose female breast nipples.
"Please be sure the genital region is adequately covered so that there is no visible 'puffy' bare skin exposure."
Artists have also reportedly been told that clothing promoting bands or featuring foreign languages must be pre-approved.
Justin Timberlake, Frank Ocean, Elton John, Ed Sheeran, Bruno Mars and Sting are among the male performers expected for the Grammys.
Presenters include Beyoncé, Carly Rae Jepsen, Katy Perry, Jennifer Lopez, Ellen DeGeneres, Ryan Seacrest and Prince.