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Objectives: We evaluated urine propylene glycol (PG) and vegetable glycerin (VG) as potential markers for discriminating e-cigarette (ECIG) users and non-users and verifying ECIG abstinence. Methods: We analyzed urine samples from 51 ECIG users (collected pre-/post-12-hour ECIG abstinence), and 50 controls (nicotine/tobacco non-users) urine cotinine, PG, and VG concentration. Results: Of 42 ECIG users with pre-abstinence urine cotinine indicating nicotine use, mean (SD) urine cotinine concentration was 1053.7 ng/ml (874.5) and for controls was 1.93 ng/ml (0.4); after abstinence, ECIG users' mean cotinine decreased to 615.4 ng/ml (753.0). For ECIG users, mean urine PG pre-abstinence was 25.6 mcg/ml (20.0) and was 9.8 mcg/ml (13.5) for controls; after abstinence, ECIG users' mean urine PG decreased to 9.7 mcg/ml (15.0; ps < .05). For ECIG users, mean urine VG pre-abstinence was 7.5 mcg/ml (7.1) and was 13.2 mcg/ml (25.0) for controls; after abstinence, ECIG users' mean VG decreased to 5.0 mcg/ml (4.4; ps < .05). Conclusions: ECIG users' mean urine PG was greater than controls and decreased after 12-hour ECIG abstinence suggesting urine PG may be useful for discriminating ECIG users from non-users and verifying short-term abstinence. [ABSTRACT FROM AUTHOR]