Upon administering the South Oaks Gambling Screen to 328 clients with substance dependence problems in treatment facilities in Windsor, Ontario, it was found that high rates of pathological gambling occur comorbidity with substance dependence. Levels of problem and pathological gambling were found to be consistent with similar studies done in North America. Treatment professionals are urged to screen for pathological gambling when treating other addictions, as this growing cormorbid addiction can compound problems when undetected.