Although various degrees of sleep alterations were reported after ischemic events in both humans and experimental animals, their clinical importance is usually neglected in context of the other, more severe, neurological abnormalities. The aim of this study was to experimentally test whether sleep alterations occur even after a minimal ischemic cerebral injury. Specifically, we investigated the changes in sleep following a 5-minute transient global cerebral ischemia (GCI) in the rat, which is known to cause only a small ischemic injury of the hippocampus. Experiments were carried out in freely moving adult male Wistar rats, accommodated to a 12h dark/light cycle. A telemetric device was implanted for wireless EEG and neck EMG recordings. After 2 days of baseline telemetric recordings, GCI was induced using a variation of the "4-vessel occlusion" model under chloral-hydrate anesthesia, and recordings were continued for at least 2 more days. To avoid the effects of anesthesia recovery, the first 12 hours recordings following GCI were excluded from the analysis. Consecutive 5s epochs were scored into wakefulness, slow-wave sleep and REM sleep. Our principal finding was that following GCI, there was an increase in total slow-wave sleep time which attenuated its variability between the light and dark cycle period. Our data suggest that even a minimal cerebral ischemic injury leads to sleep-cycle alterations in rat. This opens the possibility that prognostic markers of ischemic injury can be derived from quantifying early sleep patterns.