Abstract Introduction It has been established that the use of opioids suppresses stage N3 sleep. For individuals with opioid use disorder (OUD), medication-assisted treatment (MAT) is a widely employed opioid replacement therapy used to mitigate withdrawal effects and drug cravings. We investigated sleep architecture in individuals receiving methadone-based MAT. Methods N=6 individuals (aged 43.8±12.8y; 5 females), who were within 90 days of methadone initiation, underwent in-laboratory overnight polysomnography (8h TIB; 22:00-06:00). Prior to bedtime, pain intensity and opioid withdrawal symptoms were assessed using the Numeric Pain Rating Scale (0-10) and the Clinical Opiate Withdrawal Scale (0-48). Sleep recordings were scored visually according to AASM guidelines. Results In this sample, subjects exhibited 87.4-93.0% (M: 92.2%) sleep efficiency (SE), 8.0-16.2min (M: 12.1min) sleep latency (SL), 5.5-7.5% (M: 6.5%) N1, 46.4-52.7% (M: 49.6%) N2, 20.7-30.6% (M: 25.6%) N3, 17.5-19.1% (M: 18.3%) REM, 28.0-38.5min (M: 33.3min) N3 latency, and 84.1-125.9min (M: 105.0min) REM latency. Subjects reported moderate pain intensity scores of 5-6 (M: 5.3) and mild to moderate withdrawal symptoms of 1-15 (M: 7.8). Conclusion Relative to published healthy sleeper norms, subjects showed more N1 and N3 and less REM sleep. The increased N3 was unexpected given that opioids (such as methadone) typically suppress N3; it may reflect subjects carrying a substantial sleep debt. Pain and withdrawal symptoms may be a factor increasing N1 and reducing REM sleep. Such potential sleep deficiencies may interfere with subjects achieving OUD recovery goals and are worthy of further investigation. Support Supported in part by a seed grant from the Washington State University Office of Research Advancement and Partnerships.