EEG measures have been shown to differ in human subjects who are at genetically increased risk for the development of alcoholism. In the present study, EEG was recorded in rats that were selectively bred for alcohol-preferring (P) and nonpreferring (NP) behaviors during an ethanol self-administration paradigm. In this paradigm, rats initially learned to press a lever for a 0.2% saccharin solution. Ethanol was then added to the saccharin solution in increasing concentrations while saccharin was faded progressively. EEG recordings were analyzed under three different conditions: baseline, 0.2% saccharin and 10% ethanol. Statistical analyses were carried out within each group of rats for three 10-min intervals in each condition. NP rats showed increases in EEG power in the 6-32 Hz frequency ranges 20-30 min following ethanol availability. In contrast, no significant EEG effects were found for P rats in the 10% ethanol condition with respect to time. EEG power in the three time periods (0-10, 10-20, 20-30 min) was also compared between conditions (baseline, saccharin, 10% ethanol). For NP rats, a significant increase in EEG power during the 20-30 min time interval was found in the 10% ethanol session for the 16-32 Hz frequency range as compared to baseline and saccharin. In P rats, a significant increase in the power of the EEG was found during the first 10 min in the 10% ethanol session in the 8-16 Hz frequency range as compared to baseline and saccharin. The two rat lines also differed in their behavioral responses to the self-administration paradigm.(ABSTRACT TRUNCATED AT 250 WORDS)