The controversy about timing of cleft palate surgical procedures is focused on early palatoplasty for improved speech versus delayed hard palate repair for undisturbed facial growth. Timing and technique of palate repair are the most important influences on speech and facial growth, yet there is no consensus on the age or technique for surgery. The Oxford Cleft Palate Study was initiated to evaluate critically the long-term follow-up of 44 patients with early versus late closure of the hard palate. A multidisciplinary approach was used to determine the incidence of speech deficiencies, palatal fistulas, maxillofacial growth disturbances, and hearing abnormalities and to assess objectively the long-term effects of two different treatment modalities on the cleft palate patient. The 44 patients were selected randomly, interviewed, and examined by the multidisciplinary Oxford Cleft Palate Study team. The average age at follow-up in the early closure group was 17.0 years versus 18.2 years in the late closure group. There was a similar number of unilateral and bilateral clefts in both the early and late closure groups. The hard palate was closed in the early group at an average age of 10.8 months versus 48.6 months in the late closure group. All operative procedures in each group were performed by the same senior plastic surgery consultant. Both consultants have since retired and did not participate in the study. Each patient was evaluated by the same plastic surgeon, speech pathologist, orthodontist, and otologist. All examiners were blinded in that they were unaware of the type or timing of the surgical technique and had no prior knowledge of or access to the patient's medical records. Furthermore, none of the examiners participated in the initial care and surgery of these patients. Statistically significant greater speech deficiencies were noted with delayed hard palate closure, especially in articulation, nasal resonance, intelligibility, and substitution pattern assessment (overall intelligibility, p < 0.01). Likewise, the persistent palatal fistula rate in the late closure group was 35 percent in comparison with 5 percent for the early closure group (p <0.02). No significant differences in hearing or maxillofacial growth impairment were delineated in either group. Our data suggest that delaying hard palate closure results in significant speech impairment without a beneficial maxillofacial growth response.