Introduction: The monobloc (or frontofacial) osteotomy and advancement is an effective procedure for correction of midface hypoplasia and forehead retrusion but is known to have significant morbidity. It is unknown whether gradual lengthening by distraction osteogenesis (D.O.G.) reduces morbidity by decreasing the large dead space between the nasopharynx and supradural space of the frontal lobe. To investigate this we compared outcomes of patients who had monobloc osteotomies with acute advancement and bone grafting with patients who had D.O.G. Methods: Three groups of patients (n=30) with midface hypoplasia and forehead retrusion underwent monobloc osteotomy and advancement from !979-2001. Group 1 underwent acute advancement with bone grafting (n=13, 1979-1989). Group 2 also underwent acute advancement and bone grafting but with modification of the technique with use of pericranial flap and fibrin glue and the exclusion of patients with VP shunts (n=7, 1989-1996). Group 3 had gradual lengthening with D.O.G. using an internal device (latency=5 days, rate=1mm/day, rhythm=every 12 hours) (n=10, 1996-2001). Variables considered on retrospective review of morbidity and mortality included: age, comorbidity, previous surgery, operative time, degree of advancement, blood transfusion and presence of VP shunt (Fischer exact test was used). Serial cephalograms were also reviewed. Results: Patients were treated between 4.5 years and 10 years of age (patients under 6 years had early surgery for functional problems such as upper airway obstruction or loss of eye protection). Group 3 patients (D.O.G.) had a mean advancement 3.5mm and 3.0 mm greater than Group 1 and Group 2, respectively. Group 1 demonstrated the highest morbidity: meningitis=5 (38%), CSF leak=3 (23%), wound infection=5 (38%), transfusion reaction=1 (.7%). In contrast, Group 3 (D.O.G.) had the lowest morbidity meningitis=0 (0%), CSF leak=0 (0%), wound infection=2 (20%), transfusion reaction=0 (0%). The number of patients with any morbidity within each group was: Group1=8 (61%), Group 2=3 (43%) Group 3=2 (20%). A clinically significant difference would require a larger sample size (n=100). Conclusion: These data suggest that advancement of monobloc osteotomy by D.O.G. has less morbidity and may have less relapse that traditional acute advancement and is an alternative to staging this advancement with a fronto-orbital advancement followed by a Le Fort III advancement.