In a randomized, controlled trial, a national sample of smokers of Light cigarettes heard by telephone a "radio message" counter-marketing Light cigarettes. This message caused immediate changes in beliefs. Follow-up telephone interviews were done about 7 months later. The Message Group (N = 181) was more likely than the Control Group (N = 85) to report that (a) one Light equaled one Regular in tar yield to smokers, (b) Lights did not decrease health risks, and (c) they wanted to give up smoking (P<.05); they did not report greater quitting or intention to quit, or greater knowledge of filter ventilation. Systematic counter-marketing of Lights is recommended. A telephone-based exposure and follow-up procedure could be a good way to study message effects.