Preoperative nasoalveolar molding (NAM) in combination with primary gingivoperiosteoplasty (GPP) reduces the need for secondary alveolar bone grafting by 60% in patients with unilateral cleft lip and palate (CL/P). Herein, we investigate the efficacy of NAM and primary GPP in patients with bilateral CL/P. All patients (n = 38) with bilateral CL/P who underwent NAM and primary GPP from 1988 to 1998 with at least 14 years of follow-up were included in this study. Panoramic and periapical radiographs were used to assess dentoalveolar bone formation. A total of 38 patients were identified with median follow-up of 18 years (range 14-26 years). Of the 27 patients who underwent bilateral GPP, 14 (51%) patients had successful dentoalveolar bone formation bilaterally and 13 (49%) had unilateral bone formation. No patient had a bilateral failure. Of the 11 patients who underwent unilateral GPP, 7 (63%) patients had successful dentoalveolar bone formation. Bilateral successful dentoalveolar bone formation following primary bilateral GPP has a dependent probability of 52% and a conditional probability of 82%.