The development of dentate electroencephalographic (EEG) activity and motor behavior was studied in the neonatal rabbit. Using a combined longitudinal, cross-sectional design, neonatal rabbits were implanted with microelectrodes in the dentate region of the hippocampal formation. Recordings of electrical activity were made during the occurrence of spontaneous behaviors, during the presentation of sensory stimuli, and during the administration of eserine and atropine sulfate. Motor activities developed in parallel with the dentate EEG activity. Lowamplitude irregular activity accompanied the uncoordinated motor behaviors of rabbits 6 to 7 days of age. By 8 days, the EEG-behavioral correlation described by Vanderwolf became evident: certain types of movement were always accompanied by theta activity (type 1) whereas other types (including immobility) were accompanied by irregular activity. By 14 days of age, a second lower-frequency theta (type 2) developed. Type 2 theta occurred while the rabbit was immobile, spontaneously during the presentation of sensory stimulation (whistles, claps, and pure tones), and after the administration of the anticholinesterase drug, eserine. Administration of the anticholinergic drug, atropine sulfate, completely abolished type 2 theta activity. It was also demonstrated that in very young rabbits (between 8 and 15 days of age) atropine sulfate was nonselective in its effects, abolishing both movement-correlated theta (type 1) and immobility-related theta (type 2). Observations of REM sleep also demonstrated that theta activity first appeared at 8 days of age. Both types of theta showed a developmental increase in amplitude and frequency, attaining adult values by 23 days of age. Finally, the study supported previous findings that the dentate area of the hippocampal formation is one of the main generators of theta activity, and is capable of producing both types of theta.