Null zones and head postures were studied in two patients with idiopathic congenital nystagmus who had been carefully selected from a larger group of patients who had nystagmus with compensatory head postures. Oculomotor and sensory features of the two patients indicated that they would have a reasonable chance of profiting from surgery. Neither patient had a periodic alternating or manifest latent nystagmus or any ocular disease of the fixating eye. Postoperative evaluation of the head posture and the nystagmus behavior of both patients was carried out over a period in excess of 6 years. Neither of the patients readopted a head turn, and visual acuity was found to be equivalent to that prior to surgery when using the null zone. In one of the patients the postoperative null zone was located in the primary position, while in the other the null zone was decreased from an eccentricity of 30 degrees to 15 degrees. These results suggest that the position of the postoperative null zone is not always an accurate predictor of head turn.