The inclusion of pathological gambling (PG) in DSM-III was a watershed event for the field of gambling studies. Although research is lacking into the circumstances, both the literature and popular opinion credit the advocacy of Robert Custer as solely responsible. There is also little known about the creation of the category of impulse disorders into which PG was placed. The author searched the archives of the American Psychiatric Association, Gamblers Anonymous, and the National Council on Problem Gambling, and interviewed Robert Spitzer, who chaired the DSM-III Task Force, and other key participants. The category of impulse disorders, it was concluded, were heir to the monomanias and owe much to Esquirol’s early 19th century classification. Custer played no role in the decision to include PG in DSM-III. His actual contribution was arguably more important. He tried to avoid the conceptual problems that preoccupied the rest of the committee by focusing on the progression and harmful consequences. He presented a dynamic model that differed from the snapshot offered for the other disorders. It fit the definition of an addiction. Nevertheless, the contradictions and unresolved issues in the chapter lent confusion to the conceptualization of PG, where it belonged and what it was.