Pathological Gambling Disorder (PGD) is internationally prevalent and contributes to significant disruption and impairment in a gambler's life. For accurate diagnosis and treatment planning, clinicians require standardized criteria as in commonly used DSM and ICD-10 taxonomies, which are conceptually clear, valid, and culturally appropriate. We aimed to describe clinical issues, other than DSM criteria, that may be potentially clinically meaningful to PGD assessment and treatment planning. Participants from St. Louis, Missouri, USA, who self-identified as problem or pathological gamblers or who had a friend or relative with a gambling problem, as well as clinicians with addictions and PGD diagnostic expertise, participated in one of ten focus groups as part of a larger psychometric study aimed at developing and refining a structured, diagnostic gambling assessment tool, the Gambling Assessment Module (GAM[C]). A content-driven immersion-crystallization qualitative approach yielded insight into gambling behaviors, terminology, and diagnostic issues. While complementary to existing diagnostic taxonomies, these findings provide additional item specification for in-depth clinical assessment.