Cycloscopic analyses of a series of electroencephalograms obtained from a mixed group of individuals, clinically classified as normal, schizophrenic, and "frank" epileptic, show the following characteristics: 1. A rather closely regulated potential oscillation which remains predominant throughout the sample of record under study. 2. Associated with this dominant cycle other definite anharmonic cycles are clearly evident. These associated cycles may operate in intermittent sequences or simultaneously with the dominant cycle. Subjects with "atypical" epilepsy show an apparently characteristic spread of low intensity cycles.