Using crystal methamphetamine increases the risk for unsafe sex and HIV transmission, a new California prevention campaign warns gay men.

The Advocate reported March 15 that the $11-million campaign will include billboards, ads on public transportation and cable TV, and a website, Menotmeth.org. The latter will include video testimonials from gay methamphetamine users.

California researchers found that more than half of gay and bisexual men have used meth, compared to 5 percent of the general population.