Data collected from human studies suggests a relationship between a disruption of the septopremaxillary ligament (SPL) attachment and midfacial hypoplasia in complete cleft individuals. The present study investigates the SPL-traction mechanism and midfacial growth in a chimpanzee animal model. Seventeen chimps (7 unoperated controls, 5 shams, and 5 animals with early SPL reaction) were used in the present study. Lateral head x-rays and dental study models were collected quarterly through 1200 days of age. Growth rates (slopes of the linear growth components) were statistically compared across groups. Premaxillary growth rates were significantly (p less than 0.001) reduced in SPL resected animals compared to the other groups. Maxillary growth rates were significantly reduced in both SPL and sham animals compared to unoperated controls. No significant differences were noted for midfacial height. We conclude that SPL resection produced a significant effect on anterior midfacial growth independent of surgical trauma. These data support the concept of early reestablishment of the SPL in primary nasolabial cleft repair.