BACKGROUND: Most patients with myelodysplastic syndromes (MDS) describe difficulty sleeping (Luskin et al Br J Haem 2017) and sleep disturbance is a likely contributor to the fatigue experienced by patients with MDS and acute leukemia. Data are sparse regarding the sleep of this patient population as formally assessed with sleep-focused survey instruments. METHODS: We surveyed consecutive adult patients with MDS, AML or ALL at the Dana-Farber Leukemia clinic. With permission from the treating oncologist, patients with a physician-assessed life expectancy ≥ 12 weeks were mailed a questionnaire packet assessing insomnia symptom severity (Insomnia Severity Index; ISI), sleep quality (Pittsburgh Sleep Quality Index; PSQI), obstructive sleep apnea risk (STOP-Bang), and depressive symptoms (Patient Health Questionnaire-9; PHQ-9). Respondents underwent concomitant medical record review. RESULTS: Of 332 eligible patients contacted, 158 (47.6%) responded. Responders were 56% male with a median age of 67 years. Overall, 42% of patients reported insomnia symptoms (ISI ≥10) with the prevalence of such symptoms similar among patients with MDS and acute leukemia (48% vs 38%, p=0.23). OSA risk was high (58%), particularly in patients with MDS (67% vs 52% p=0.10). Those with high OSA risk were more likely to have clinical insomnia as defined by ISI ≥10 (OR 2.6, p=0.01). Depression was uncommon: only 7% had PHQ-measured moderately severe or severe depression. Median sleep duration for the entire cohort was 6.9 hours (range 3-12) indicating that over half of respondents slept less than the 7 hours per night recommended by the National Sleep Foundation for healthy adults. Poor sleep quality (PSQI "Bad Sleep") was seen in 79% of the overall cohort. CONCLUSION: When measured with validated tools, disturbed sleep is common among patients with MDS and acute leukemia. OSA risk is also prevalent but does not likely explain all of the poor sleep quality seen. These data suggest that strategies are needed to improve both quantity and quality of sleep in this population. Table Disclosures DeAngelo: Abbvie: Research Funding; GlycoMimetics: Research Funding; Blueprint: Consultancy, Research Funding; Amgen: Consultancy; Celgene: Consultancy; Shire: Consultancy; Incyte: Consultancy; Novartis: Consultancy, Research Funding; Takeda Pharmaceuticals: Consultancy; Jazz Pharmaceuticals Inc: Consultancy; Pfizer: Consultancy. Garcia:Abbvie: Research Funding; Genentech: Research Funding. Winer:Jazz Pharmaceuticals, Pfizer: Consultancy. Steensma:Aprea: Research Funding; Arrowhead: Equity Ownership; Pfizer: Consultancy; H3 Biosciences: Other: Research funding to institution, not investigator.; Astex: Consultancy; Onconova: Consultancy; Stemline: Consultancy; Summer Road: Consultancy.