Twenty-one patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) were classified into three categories according to their pharyngeal stenosis patterns during sleep, as determined from endoscopic findings: (i) a falling type (n = 6); (ii) an all-round type (n = 11); and (iii) a bilateral type (n = 4). In all patients with the bilateral type, the palatine tonsils were hypertrophied, and the apnea-hypopnea indexes (AHI) were improved markedly by surgery. Conversely, the AHI of patients with the falling and all-round types were reduced by a smaller percentage. Surgical therapy is only to be recommended to patients with OSAHS whose pharynx is bilaterally stenotic.