Study Objectives:To evaluate the effects of single doses of gabapentin 250 and 500 mg on polysomnographic (PSG) and participant-reported sleep measures in a 5-h phase advance insomnia model. Methods: Adults reporting occasional disturbed sleep received gabapentin 500 mg (n = 125), 250 mg (n = 125), or placebo (n = 127) 30 min prior to bedtime and were in bed from 17:00 to 01:00, ~5 h before their habitual bedtime. Sleep was assessed by PSG, post-sleep questionnaire, and the Karolinska Sleep Diary (KSD greater and percent stage 1 (15.1%, 11.8%, and 10.8%, respectively) signifi cantly lower relative to placebo. Gabapentin was associated with signifi cantly higher values of KSD Sleep Quality Index and reported TST versus placebo; no other reported outcomes were signifi cant. Neither gabapentin dose produced evidence of next-day residual effects as measured by DSST and SSS. Adverse events were infrequent (< 5%). Conclusion: Participants with occasional disturbed sleep treated with gabapentin showed signifi cantly longer sleep duration and greater depth (versus placebo) in response to a phase advance manipulation known to disrupt sleep maintenance.