The Guerrilla Girls is a group of feminist artists established in New York City in 1985 and is known for using guerrilla art) to promote women, and minorities, in the arts. Their traditional tactics included putting up posters decrying the gender and racial imbalance of artists represented in galleries.
One of their most famous posters was plastered across New York City buses in 1989. Its headline read, “Do women have to be naked to get into the Met. Museum?” According to the Guerrilla Girls, they conducted a “weenie count” at New York’s Metropolitan Museum of Art and found that less than 5% of the artists in the Met’s Modern Art sections were female, but 85% of the nudes were female.

http://www.guerrillagirls.com/