OBJECTIVE: In this study, we assessed the efficacy of a new method (expansion sphincter pharyngoplasty [ESP]) to treat obstructive sleep apnea. STUDY DESIGN: We conducted a prospective, randomized controlled trial. METHODS: Forty-five adults with small tonsils, body mass index less than 30 kg/m 2 , of Friedman stage II or III, of type I Fujita, and with lateral pharyngeal wall collapse were selected for the study. RESULTS: The mean body mass index was 28.7 kg/m 2 . The apnea-hypopnea index improved from 44.2 ± 10.2 to 12.0 ± 6.6 ( P < 0.005) following ESP and from 38.1 ± 6.46 to 19.6 ± 7.9 in the uvulopalatopharyngoplasty group ( P < 0.005). Lowest oxygen saturation improved from 78.4 ± 8.52% to 85.2 ± 5.1% in the ESP group ( P = 0.003) and from 75.1 ± 5.9% to 86.6 ± 2.2% in the uvulopalatopharyngoplasty group ( P < 0.005). Selecting a threshold of a 50% reduction in apnea-hypopnea index and apnea-hypopnea index less than 20, success was 82.6% in ESP compared with 68.1% in uvulopalatopharyngoplasty ( P < 0.05). CONCLUSION/SIGNIFICANCE: The ESP may offer benefits in a selected group of OSA patients.