Problems initiating and maintaining sleep, and waking up exhausted have been implicated as precursors of a first nonfatal myocardial infarction. These sleep problems are part of an array of complaints that we have labeled as reflecting a state of 'vital exhaustion.' Excess fatigue, loss of vigor, increased irritability, and feelings of demoralization are also characteristic of this state of vital exhaustion, which has been found to constitute a risk indicator for future myocardial infarction. In the present study, we tested the hypothesis that the sleep of exhausted subjects is characterized by a relative absence of slow wave sleep. To test this hypothesis, all-night recordings of the EEG, EOG, and submental EMG of nine exhausted and eight nonexhausted subjects were made for four nights. Sleep stages were rated according to standard criteria. Because these stages do not adequately reflect the essentially continuous aspect of slow wave sleep (SWS), a more detailed analysis of changes in frequencies of the EEG during sleep was also made, using spectral analysis. It seemed that SWS was significantly diminished in exhausted subjects. This suggests that the normal restoration processes that take place during sleep are impaired in exhausted subjects. Additional studies are required to determine the significance of this finding with respect to cardiovascular control during sleep.