GABAergic, sleep-active neurons in the preoptic hypothalamus are key components of hypothalamic-brainstem circuits that regulate sleep and arousal. Many sleep-active neurons recorded in the median preoptic nucleus (MnPO) and the ventrolateral preoptic area (VLPO) exhibit elevated discharge rates during both nonREM and REM sleep compared to waking. A population of neurons in the dorsal lateral preoptic area (DLPO) exhibit REM-active discharge. Preoptic nonREM/REM-active neurons may participate in control of the nonREM-REM cycle. To evaluate this, we examined projections of GABAergic neurons in the preoptic area to midbrain nuclei implicated in REM sleep control, the ventrolateral periaqueductal gray (vlPAG) and the dorsal raphe nucleus (DRN). Adult Sprague-Dawley rats received unilateral injections of the retrograde anatomical tracer, cholera toxin subunit-b Alexa Fluor 594 conjugate (CTb), targeting the vlPAG or DRN. After a 14-day survival period to allow for retrograde transport of tracer, rats were euthanatized and tissue sections through the preoptic hypothalamus were processed for visualization of CTb and of glutamic acid decarboxylase (GAD), a marker of GABAergic neurons. CTb injections that successfully targeted the vlPAG resulted in a moderate density of CTb-labeled cell bodies in the VLPO with co-localization of GAD occurring in ~30% CTb+ neurons. The density of CTb labeling in the MnPO and DLPO was somewhat lower, with co-localization of GAD occurring in ~15–20% of CTB+ neurons. CTb injections in the DRN yielded moderate to high density of retrogradely labeled neurons in the VLPO, with co-localization of GAD in ~40–50% of CTb+ neurons. Compared to VLPO, co-localization of CTb and GAD in the MnPO and DLPO was low. This study confirmed anatomical connections between GABAergic neurons in sleep-regulatory regions of the preoptic area to REM sleep-regulatory regions in the midbrain, with the highest density of GABAergic projection neurons originating in the VLPO. These connections may functionally integrate neuronal systems that control sleep onset and nonREM sleep to brainstem REM sleep generating circuits. Supported by the Department of Veterans Affairs (Grant BX00155605) and the National Institutes of Health (Grant R01-NS092383).