Objective To determine whether hot flashes produce disordered sleep i n symptom atic postmenopausal women. Design Controlled laboratory study. Setting Healthy v olunteers in a university medical center. Patient(s) Symptomatic and asymptomati c postmenopausal women and premenopausal women, all of similar ages (46-51 year s). Intervention(s) None. Main outcome measure(s) Sleep electroencephalogram rec ordings, sternal skin conductance to record hot flashes, multiple sleep latency test to assess sleepiness, simple and divided attention performance tests, sleep and fatigue questionnaires. Result(s)-Nineteen women were not selected for the following reasons: seven failed the drug screen, two had sleep apnea and period ic limb movements, one had periodic limb movements alone, two had body mass inde x (BMI) >30, one had hypertension, and six asymptomatic women had hot flashes in the laboratory. There were no significant group differences on any sleep stage measure. For example, for cycling vs. symptomatic vs. asymptomatic women: total sleep time, 6.9 ±0.7, 7.0 ±0.4, 7.0 ±0.4 hours; percentage stage 1 (light) sl eep, 9.3%±4.2%, 10.4%±2.5%, 10.5%±3.9%; number of brief arousals, 89.6 ±30.1, 111.9 ±45.8, 99.4 ±22.2; number of awakenings, 4.8 ±3.3, 6.7 ±2.1, 6 .9 ±3.5. An average of 5.2 ±2.9 (±SD, range 1-18) hot flashes/night occurred in the symptomatic women. Of arousals occurring within 2 minutes of a hot flash , 46.7%occurred before, 46.7%occurred after, and 5.6%occurred simultaneously. Of awakenings occurring within 2 minutes of a hot flash, 55.2%occurred before, 40.0%after, and 5%simultaneously. There were no significant group differences on the multiple sleep latency test or any performance test or questionnaire mea sure. Conclusion(s) These data provide no evidence that hot flashes produce slee p disturbance in symptomatic postmenopausal women. Previous reports of increased sleep disturbance at menopause may be due to disorders that were screened out, such as sleep apnea and drug use. Objective Control of hot flashes produce disordered sleep in symptom atic postmenopausal women. Design Controlled laboratory study. Setting Healthy v olunteers in a university medical center. Patient (s) Symptomatic and asymptomati c postmenopausal women and premenopausal women, all of similar ages -51 year s). Intervention (s) None. Main outcome measure (s) Sleep electroencephalogram rec ordings, sternal skin conductance to record hot flashes, multiple sleep latency test to assess sleepiness, simple and divided attention performance tests, sleep and fatigue questionnaires (S) -Nineteen women were not selected for the following reasons: seven failed the drug screen, two had sleep apnea and period ic limb movements, one had periodic limb movements alone, two had body mass inde x (BMI)> 30 , one had hypertension, and six asymptomatic women had hot flashes in the laboratory. There were no significant group differences on any sleep stage measure. For example, for cycling vs . Symptomatic vs. asymptomatic women: total sleep time 6.9 ± 0.7, 7.0 ± 0.4, 7.0 ± 0.4 hours; percentage stage 1 (light) sl eep, 9.3% ± 4.2%, 10.4% ± 2.5%, 10.5% ± 3.9% ; number of brief arousals, 89.6 ± 30.1, 111.9 ± 45.8, 99.4 ± 22.2; number of awakenings, 4.8 ± 3.3, 6.7 ± 2.1, 6.9 ± 3.5. An average of 5.2 ± 2.9 (± SD, range 1-18 Of arousals occurring within 2 minutes of a hot flash, 46.7% occurred before, 46.7% occurred after, and 5.6% occurred simultaneously. Of awakenings occurring within 2 minutes of a hot flash, 55.2 % occurred before, 40.0% after, and 5% simultaneously. There were no significant group differences on the multiple sleep latency test or any performance test or questionnaire mea sure. Conclusion (s) These data provide no evidence that hot flashes produce slee p disturbance in symptomatic postmenopausal women. Previous reports of increased sleep disturbance at menopause may be due to disorders that were screened out, such as sleep apnea and drug use.