The BLP allows researchers, educators, and administrators to quickly and easily gather information about the functional language abilities of bilingual populations. The instrument assesses language history, proficiency, use, and attitudes in the two languages of bilinguals through self-reports. The measures can be used to develop a profile of speakers’ relative language dominance. Designed for ease of use, the instrument can be administered by a non-specialist, takes less than 10 minutes to complete, and is available as an online questionnaire through Google Docs. It can be adapted to specific needs by emphasis on appropriate subtests within the instrument.