This study will examine extended exposure to cigarettes varying in nicotine content among opioid abusers. Prevalence of smoking among opioid-dependent adults far exceeds that of the general US adult population. Opioid-dependent smokers are also at elevated risk for smoking-related adverse health effects. Studies testing an innovative regulatory strategy of reducing the nicotine content of cigarettes to a non-addictive level have shown promising beneficial effects (decreased smoking rate, reduced toxicant exposure, and increased cessation) in the general population of smokers. However, these studies have uniformly excluded vulnerable populations like opioid abusers who may respond differently considering their greater vulnerability to smoking and nicotine dependence. Thus, little is known scientifically about how this highly vulnerable subgroup of smokers might respond to a nicotine reduction policy. This project is designed to address that substantial knowledge gap.