The first edition of Heroin Addiction: Theory, Research, and Treatment was published in 1976, and the second edition in 1986. The second edition was designated Volume 1 at the time of a second printing in 1988, with the intent of initiating a series of volumes at appropriate intervals to inform readers of rapidly unfolding developments in the field. Thus, Volume 2 provides an overview of new findings with respect to the understanding of heroin and their application to the development and improvement of treatment.