Comments on an article by N. el-Guebaly et al. (see record 2012-24821-004). The authors present evidence that pathological gambling (PG) is a condition that shares more phenomenological, neurobiological, psychological and treatment-related commonalities with substance use disorders (SUDs) than with obsessivecompulsive disorder (OCD). The concept of compulsivity is useful for communication between clinicians, it is too ambiguous and confusing for research studies of the topic. Secondly, while several well-validated clinical and research instruments are available for measuring impulsivity, similar instruments for measuring compulsivity are almost non-existent. Thirdly, compulsivity (like impulsivity) may be an unstable 'moving target', meaning that it cannot be an 'endophenotype' per se which, by definition, is an enduring trait that is unrelated to illness state or stage. Finally, individual differences in clinical presentation and treatment response are often the rule rather than an exception. The author begins to provide empirical foundations to guide these decisions and facilitate better delineation of the 'boundaries' in future conceptualizations.