The present study tested the feasibility of an Internet-based method to obtain objective evidence of smoking abstinence and to deliver vouchers for evidence of abstinence. Four heavy smokers participated in this 4-week study. Twice daily, participants made video recordings of themselves providing a breath carbon monoxide (CO) sample with a Web camera. The video was sent electronically to the smoking clinic. Participants could earn vouchers for gradual reductions in breath CO during an initial shaping condition, and then for achieving abstinence (CO [less than or equal to] 4 ppm). Vouchers could be exchanged for merchandise at select Internet vendors. Relative to baseline conditions, participants substantially reduced their smoke intake, and 3 achieved sustained periods of abstinence. The study suggests that an Internet-based voucher reinforcement program is a feasible method to promote abstinence from cigarette smoking.