Comments on craving.

This brief commentary addresses a few issues relevant to the conceptualization and assessment of craving. It begins by suggesting the utility of the analogy between craving and hunger, another often-studied subjective experience with presumed motivational significance. It then proceeds to a discussion of procedures for assessing craving, highlighting the limitations of retrospective reports, and the potential utility of real-time measures. Finally, building upon the findings of such real-time measures, it suggests the need to differentiate tonic and phasic craving experiences.