Deep and surface electroencephalograms were recorded during sexual arousal culminating in orgasm in 2 patients, 1 undergoing treatment for severe mental illness and the other for intractable epilepsy. Such recordings were obtained on two occasions in 1 patient and on 12 occasions in the other. Recording changes concomitant with the behavioral response were significant and consistent; most striking was the appearance of spike and slow-wave with superimposed fast activity in electroencephalograms from the septal region during sexual orgasm. In one patient distinct, but less dramatic, changes also occurred in the amygdalae, thalamic nuclei, and deep cerebellar nuclei. The other brain sites in which changes occurred are anatomically connected to the septal region and have previously been shown to be important sites in the pathways for emotional expression. These data substantiate previously reported data, gathered through other procedures, of a consistent correlation between activity in the septal region and the pleasure response.