Craving and anxiety share many similar attributes including comparable responses to pharmacological agents. To better characterize the relationship among craving, anxiety, and other opioid withdrawal signs and symptoms, we examined 32 opioid-dependent subjects undergoing clonidine-assisted opioid withdrawal. A 13-item analog scale measured subjective withdrawal symptoms. Statistical analyses of separate subscale items, using craving as the dependent variable, showed that the highest positive correlations occur for craving and anxiety. The high correlation between craving and anxiety suggests common mechanisms underlying both.