A concomitant analysis of sleep and feeding patterns in 11 male Wistar rats was carried out over 8 days, using continuous EEG recording. The proportion of slow-wave sleep and paradoxical sleep within an intermeal interval was constant and varied only in relation to the time of the day. During the dark period only, there were significant correlations between meal size and amount of time spent in both stages of sleep in the following intermeal interval. These correlations were even stronger between meal size and sleep duration in the intermeal interval that followed the next meal. Circadian variations in satiety ratios (i.e., units of subsequent intermeal interval and sleep per units of food ingested) and in deprivation ratios (i.e., units of feeding per units of prior intermeal interval and sleep) suggest that division of 24-hr data into 3 8-hr periods rather than 2 12-hr periods reveals distinct correlations between meal size and pre- and postmeal sleep and might reflect more accurately the underlying metabolic events. (34 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1979 American Psychological Association.