100% naphthalene! Wow, I didn't know that. Organic gardeners and alternative-health practitioners all say not to use moth balls. My mom used to put moth balls in all our woolens. I loved the smell. When she would take our woolens out for winter, I'd nestle my face in them and breathe in the vapors. ARRGGH! It's amazing that our generation is still alive. We were sprayed with DDT, too, to get rid of mosquitoes. Of course, there's a lot of hype about those chemicals, too, that isn't realistic. DDT, when used properly, is one of the best deterrents for malaria carrying mosquitoes.