We report a patient, a 30-year-old male Japanese-Brazilian migrant con
struction worker, suffering from excessive daytime sleepiness for at l
east 6 months. Electroencephalogram recordings during his waking state
s showed that 10-Hz and 60-mu V alpha activity was present prominently
in the occipital regions. From the multiple sleep latency test, it wa
s found that stages 1-2 NREM sleep episodes appeared repetitively with
out any REM episodes, and that the mean sleep latency was 10.2 min. Th
ese findings support the diagnosis that this patient suffers from subw
akefulness syndrome.