Branchio-motor activities from trigeminal, facial, glossopharyngeal and vagal nerves, in chick embryos have been recorded using suction electrodes on an isolated preparation of the hindbrain in vitro between developmental stages 20 and 36. They were composed of recurring episodes of cyclical burst discharges first identified at stage 24, therefore constituting one of the earliest organized activities generated in the chick central nervous system. Between stage 24 and 36, both the period between episodes and the number of bursts per episode were increased. This maturation sequence was preserved for several hours in vitro in the absence of supraspinal and sensory inputs. Results are in agreement with rhythmogenic properties constituting an early functional commitment of neuronal networks in this particular region of the neuroepithelium.