`` Just Say No '' was an advertising campaign , part of the United States `` War on Drugs '' , which was waged during the 1980s and early 1990s , to discourage kids from trying drugs by offering various ways of saying no. . `` Just Say No '' was an advertising campaign , part of the U.S. `` War on Drugs '' , prevalent during the 1980s and early 1990s , to discourage children from engaging in recreational drug use by offering various ways of saying no. .