The fourth volume of this series features reviews that cover a range of subjects, with authorship from the United States and European Union. The likely inclusion of craving in the DSMV criteria for addiction confers special timeliness on the paper from Stephen Tiffany ("Update on Craving"). We can now look back on addiction therapeutics, in general, and on a clinically- and financially-successful anti-addiction medication buprenorphine in the paper from Nancy Campbell and Anne Lovell. Marcus Munafo and colleagues provide an important emphasis on the ways socioeconomic status interacts with a common addiction, smoking. F. Ivy Caroll and colleagues provide an excellent update on the medicinal chemistry of new designer drugs, tracing designed drugs from the streets to the papers in which their syntheses and properties were described. The often-underappreciated role of ultrastructural information in defining circuits important for addiction is reviewed by longtime leaders in this field Mariscella Morales and Virginia Pickel. The important continuing contributions of smoking comorbidities are reviewed by Tony George and colleagues, and a framework for mouse models for smoking cessation advanced in the review by Hall, Uhl, and colleagues. NOTE: Annals volumes are available for sale as individual books or as a journal. For information on institutional journal subscriptions, please visit ACADEMY MEMBERS: Please contact the New York Academy of Sciences directly to place your order (www.nyas.org). Members of the New York Academy of Science receive full-text access to Annals online and discounts on print volumes. Please visit http://www.nyas.org/MemberCenter/Join.aspx for more information about becoming a member.