OBJECTIVE: The aim of this study was to investigate the potential of mindfulness-based stress reduction (MBSR) as a treatment for chronic primary insomnia.DESIGN: A randomized controlled trial was conducted. SETTING: The study was conducted at a university health center. PATIENTS: Thirty adults with primary chronic insomnia based on criteria of the Diagnostic and Statistical Manual of Mental Disorders, Text Revision, 4th Edition were randomized 2:1 to MBSR or pharmacotherapy (PCT). INTERVENTIONS: Mindfulness-based stress reduction, a program of mindfulness meditation training consisting of eight weekly 2.5 hour classes and a daylong retreat, was provided, with ongoing home meditation practice expectations during three-month follow-up; PCT, consisting of three milligrams of eszopiclone (LUNESTA) nightly for eight weeks, followed by three months of use as needed. A 10-minute sleep hygiene presentation was included in both interventions. MAIN OUTCOMES: The Insomnia Severity Index (ISI), Pittsburgh Sleep Quality Index (PSQI), sleep diaries, and wrist actigraphy were collected pretreatment, posttreatment (eight weeks), and at five months (self-reports only). RESULTS: Between baseline and eight weeks, sleep onset latency (SOL) measured by actigraphy decreased 8.9 minutes in the MBSR arm (P < .05). Large, significant improvements were found on the ISI, PSQI, and diary-measured total sleep time, SOL, and sleep efficiency (P < .01, all) from baseline to five-month follow-up in the MBSR arm. Changes of comparable magnitude were found in the PCT arm. Twenty-seven of 30 patients completed their assigned treatment. This study provides initial evidence for the efficacy of MBSR as a viable treatment for chronic insomnia as measured by sleep diary, actigraphy, well-validated sleep scales, and measures of remission and clinical recovery.