Phase contrast and electron microscopy was used to study the maturation of the sensory epithelia in the cristae ampullares in the rabbits. The sensory cells differentiate from the simple cylindrical cells at the time their nerve endings make synaptic contact. The afferent nerve endings in the hair cells type II have been first appeared. Then the efferent innervation in the hair cells type II and nerve chalice formation in the hair cells type I have been occurred at birth. The significance of this findings was discussed.